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Cure Sudden, or Progressive, Computer Slowing

Last reviewed: September 2005

Has your computer speed slowed substantially?

Sometimes a user finds that a previously adequate PC suddenly, or progressively, becomes unacceptably slow. The possible reasons for this are many and varied. The main causes, and their cures, are discussed on this page. They apply to all Windows versions.

Often sudden slowing is due to spyware and viruses acquired when surfing the internet, or downloading MP3's, movies, software, etc. Another main cause can be Startup programs that run automatically when you bootup. Even Windows updates can be a cause on some computers.

On this page:

This page is designed for users with a dramatic deterioration in computer performance. If your computer normally 'feels a little slow' for your needs, then you should go to the Speed Tweaks section of THPC. Those speed tweaks were written for Window 9x/Me but many tweaks also apply to Windows XP, 2000, or NT.

Identify when and where slowing occurs

Ironically your first action is to sit and think! Bootup the computer, sit back, and observe. Now, was that slower than it should be or does the slowing only appear later when running programs? Is the slowing immediate or is it progressively worse as you use software? Is it specific to the use of one program or to everything you run on the computer?

Can you relate the slowing to any specific event? This might be the installation of new hardware, a new or updated driver, or some action you took like altering software Options. In particular, have you recently installed, or altered anti-viral, software or a firewall?

Next bootup to Safe Mode (press F8 during bootup). This boots Windows with a minimum of device drivers. The problem will disappear if one of the unloaded drivers is at fault.

Spyware or Startup programs are the most likely culprits. These should be investigated first if you have been unable to identify a possible cause.

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Spyware, Adware, Malware, Trojan-Horses, Viruses

Unwanted programs are all too common now and can cause substantial slowing. If you monitor your CPU usage you may find they utilise up to 100% of CPU usage when you would expect very little usage. They can also cause crashes and Internet disconnections.

They are eliminated by using spyware or anti-viral software. The same software can prevent nasty programs from installing on your computer but care must be taken by the user - a balance must be achieved because too much protection will, by itself, slow your computer.

The latest version of the protective software must be downloaded and used to clean your system. You must then regularly download updates to keep up-to-date. Getting updates frequently is relatively painless, even on slow connections, as the download will normally be quite small.

Spyware, Adware, Malware:

In general, Spyware arrives on your computer without your knowledge. They can be responsible for pop-up ads, redirection to unfamiliar search engines, or even stealing of personal information. Users most often get them by downloading free games, or file-sharing software, or consenting to something buried in a licensing agreement.

Some of the best spyware diagnostic/removal utilities are still freeware for individual users. Run them in Safe Mode to achieve the best results. Most of these utilities leave it to the user to decide what to do with any nasty programs found. THPC always uses two spyware utilities.

Note: A security update for Windows XP SP2 warns users of spyware and other unexpected programs before they are loaded. This Windows Malicious Software Removal Tool is updated every month when you access the Windows XP updates page.

Get it Ad-Aware SE Personal (2.7 MB, freeware) from
Home site:

Get it Spybot - Search & Destroy (4.8 MB, freeware) from
Home site:

Viruses, Trojan-Horses:

Virtually every computer user will, at some stage, encounter a virus! It may come from E-Mail attachments, browsing on the Web, nasty 'free' software, a floppy disk, and a variety of other sources. A virus can be relatively harmless, can cause minor to major problems, or can totally trash your system. A boot virus may prevent your computer from booting at all. Trojan-Horses are less damaging but must still be eliminated/prevented.

Never click on anything unless you are sure of its sourse. Do not accept anything from the Web unless you initiated it you. Get your anti-viral software to check every download. Virus creators are very intelligent people and they are determined to prove it. You must create good habits for you to stay one step ahead of them.

If you eliminate a virus, you should immediately clear out any Restore points (a backup may contain the virus!), and then create a new Restore point which will now be virus-free.

When deciding on what level of protection you want from your anti-viral software, you must achieve a balance. Total protection will vet every file used but will slow your computer to a crawl. That would be total over-kill. The default settings should be adequate for most users, though some Norton users claim their settings are too severe (THPC does not confirm this).

A Firewall is a program that allows you to specify which programs have your permission to use your Internet connection. This is essential today to prevent unauthorised use of your computer by malicious software.

As a home user, THPC has used the freeware versions of AVG anti-virus and Zone Alarm firewall software for some years and fount both very satisfactory. The business community may prefer the professional versions of such products. Your anti-viral software should be updated every two weeks.

Get it AVG Free Edition (13.1 MB, freeware anti-virus) from Grisoft.

Get it ZoneAlarm (9.1 MB, freeware firewall) from ZoneLabs

Other Free Scans & Downloads:

In some cases you'll need a minimum version of a specific browser for free scans.

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Startup Programs

When you bootup your computer, it's likely a number of programs, utilities, additional Windows functions start running - even if you are sometimes unaware of this. They utilize CPU time, eat up memory, and reduce system resources. Some startup programs can cause a substantial reduction in computer performance. Removing, or taming, them can often give a huge gain in performance.

Major culprits include Anti-virus, Firewall, Instant messaging, System Agent, Find Fast, Active Desptop, Office Startup, MediaPlayer, RealPlayer's StartCenter, NetMeeting, Active Movie, Animated cursors and icons, and many others. They may be useful, but they utilise buckets of memory and resources! For instance, it's said that Norton AV and Norton Utilites together reduce performance by up to 28%!

It is highly likely you can cope very well with them all switched OFF or with reduced activity, and use them ONLY when you decide to use them. The anti-viral and firewall software are possible exceptions, though you must ensure these are not trying to do too much all the time (like testing every file before it's used!). You can read the Startup page for an explanation of how to eliminate all these unnecessary programs.

However, let's remember your objective at the moment is to identify just one, or possibly two, programs that are causing the sudden or progressive computer slowing. The guilty program most likely has an icon on the right of the Taskbar near the time. In some cases you may need to access it via Start > Programs or Program Files.

  • If the guilty program has its own "Enable on Startup", or similar, option, then you must use that program's option to disable it - or it may return later to haunt you! If such an option is not available, you can use the Microsoft Configuration Utility (MSConfig) or a freeware utility. These are described below.
  • For non-essential items that can be run by you when required, disable Startup for them all and leave them disabled.
  • For essential items, disable them temporarily while you test your system for a period of time.
    • If there's no improvement, you can re-enable them permanently.
    • If there is improvement, you must examine all options in that program to identify what's causing the slowing. Re-enable the Startup option when you have rectified the cause or you must leave it disabled.
    • If you cannot identify the specific part of the guilty program, you should consider uninstalling it and using an alternate.

Disabling a Startup Option:

  1. Stay off-line especially if testing anti-viral or firewall software.
  2. Select one program, and use these methods to look for a Startup option you can switch Off:
    Right-click the item on right of Taskbar.
    Or, look for a similar Option in Start > Programs > the software > Options. You may need to look in all the options.
    Or, use MSConfig (Select Start Run. Type in MSCONFIG, and press Enter. Click on the Startup tab)
    Or, use a freeware utility like Startup Cop or EndItAll.
  3. Disable the Startup option for that program.
  4. Reboot, and make sure the Startup option is still disabled.
  5. Run your computer normally for a period of time.
  6. If there's no noticeable improvement, select another program and repeat the procedure.
  7. When the guilty program has been located, you can re-enable Startup for other essential programs.
  8. For best performance, permentally disable Startup for all but the most essential Startup programs.

Using the Microsoft Configuration Utility (MSConfig):

MSConfig is primarily for troubleshooting and will remove an item from starting on bootup, only temporarily or perhaps permanently depending on circumstances. MSConfig is part of Windows 98, 98SE, Me, and XP. Users with NT or 2000 can use the official XP version (64 KB, free download HERE) - extract, and run it, from anywhere. Win95 users can use StartupCop (see below).

Running MSConfig:
Click Start > Run. Type in MSCONFIG, and press Enter. Click on the Startup tab. Don't forget to click Apply after you uncheck an item.

Some Startup entries are easy to identify. The majority are difficult to decipher. You'll find a very comprehensive list of entries and explanations here:

MSConfig must not be used if the software has an option to disable the startup. You must first check the program for a 'Switch off Startup' option or something similar. Otherwise the program may be re-enabled in MSConfig the next time the program is run and it's likely to pester you!

Note: Selective Mode is used (see its General tab) when MSConfig is used to disable a Startup item. If a user changes this back to Normal startup, then all disabled items will be re-enabled. So leave it at Selective Mode when MSConfig makes that alteration. Also, MSConfig may continue to run each time you reboot (it's a reminder) until you check the "Don't show this message again" check box.

System Information Utility

This Windows utility gives an even more detailed list of auto-starting programs.
Click Start > Programs > Accessories > System Tools > System Information)
Select Software Environment > Startup Programs to view any programs automatically launched by the Registry. For removal, consult each application's help file.

Startup COP

This is an excellent free comprehensive utility from PC Magazine and is much liked by many users.
Startup Cop works with Windows 95/98/Me/NT4/2000/XP.

Startup Cop helps you handle problems with programs that are automatically launched at startup by listing them and letting you disable, enable, or delete them. You can save the list of programs that are currently enabled or disabled as a profile that can be restored at a later time.

Get it (freeware; 529KB Zip file; view, disable, enable, delete startup programs). Home page: PCMag

EndItAll Utility

EndItAll is a freeware utility from PC Magazine who say:
" If you are serious about keeping your Win98 installation in tip-top shape you'll employ one of the tricks that experts use.
It is simple but effective: Close all running application, even the background stuff, before installing software. Sounds simple, but most folks aren't aware that often many programs are running in the background.
We have a solution for you. EndItAll will allow you to terminate all non-essential programs for:
1. installing new software,
2. running finicky games, or
3. writing to CD-Rs that need a big buffer. "
EndItAll can also be used prior to gaming!
Get it EndItAll (freeware, 393KB Zip file; close all non-essential programs)

For most users Spyware and/or Startup programs is the cause of sudden, severe, or progressive computer slowing.

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Make sure DMA is turned on for the hard disk(s)

This may be a shot-in-the-dark, but it's also a must-check-it-out for home users. If your IDE controller is using PIO instead of DMA, your bootup will be slow and general performance will deteriorate. This is sometimes reported after a failed game installation, a game or software crash, and for a variety of other reasons.

Checking for DMA usage:

  • Go to Control Panel > System. Locate and double-click Device Manager.
  • Expand the IDE ATA/ATAPI controllers.
  • Right-click the Primary IDE Channel, and click Properties.
  • Click the Advanced tab.
  • The Transfer Mode should be set to DMA or 'DMA if available',
    and the Current Transfer Mode should say DMA5 or a similar DMA.
  • If PIO is used, change the Transfer Mode to the DMA available.
  • Click OK, and reboot.

Advanced users can delete both the primary and secondary controller channels. Say No when asked to reboot. Close everything and reboot normally. On reboot, Windows will find, and install, the controller drivers properly and should then use the correct transfer mode.

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Bloated Registry

This may apply to you if you normally install lots of software and have not reinstalled Windows in the last year (and have not cleaned your Registry). It can even apply if you normally uninstall software correctly because there are still some software remnants and empty spaces are created!

The adage 'Windows grows and slows' is certainly true of the Registry. The Registry is a core component of Windows that stores information about your computer, including some details of all the programs installed on your system. Very often a program doesn't completely remove itself when it's uninstalled, and you end up with what is called a bloated Registry.

The more information in the Registry, the longer it takes for your computer to process data. Since the Registry operates in your computer's memory (RAM), a bloated Registry can affect nearly every aspect of your computer. This slows down the boot time as well as performance as whole. Indeed, if your bootup time appears normal, then a bloated Registry may not be your problem.

Registry cleaner utilities are used to remove unnecessary bloat from your Registry. Just as with Adware, you must always use at least two utilities to effectively clean the Registry. The following are just some of the many Registry Cleaners that are available. Most of these have an in-built Registry backup utility.

Download FREE Registry Cleaners:

RegClean 4.1a (782 KB, freeware, Microsoft/unsupported, Windows 9x, not Me/XP)

WT RegCleanerXP (886 KB, freeware, all versions of Windows).

RegCleaner (541 KB, freeware, all versions of Windows).

EasyCleaner (2.7 MB, freeware, lots of other features, all versions of Windows).

Warning: You should always backup the Registry before you use any Registry-related utility - just in case!

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Severe Hard Disk Fragmentation

Fragmentation occurs in all Hard Disks.

When you use a program some files are moved into memory and may be altered while there. When you're finished, the files are sent back to the hard disk. Now some may not fit as previously, are split up, and are stored further away on different parts of the disk - they are fragmented. In the future, accessing all these pieces from different areas of the disk will be a little slower, and then slower, and then ...

Fragmentation of, lets say, 5% may seem quite small and immaterial. However this is 5% of perhaps many gigabytes. Also it's highly likely that most fragmentation has occurred in those very files you use most frequently! If you have very severe defragmentation, like 15%, your computer will slow down and will be getting a little slower progressively - you need to use 'Defrag'.

Defragmenting these files puts them all back into neat sequential order, and they can be accessed faster. In addition, Windows 98 and later will place your most frequently accessed programs on the fastest parts of the disk. Unfortunately, fragmentation starts again immediately, so regular attention is necessary. Defragmenting is important, and especially so in low-memory computers.

Severe disk fragmentation may slow your computer by as much as 20%. This slowing is likely to be progressive rather than of sudden origin. It's cured by running a defragmentation utility, one of which is installed by all versions of Windows.

Running Windows' Disk Defragmenter:

Don't waste time defragging rubbish! Before you start Defrag, you should first remove that software you forgot to uninstall! Then remove unrequired files.

Run Disk Cleanup if your Windows version has it (Programs > Accessories > System Tools > Disk Cleanup).

Otherwise, delete your browser's Temporary Files and History. Empty all unrequired mail from your E-Mail folders and empty your Deleted Items folder. Then delete .tmp and .bak files and any unneeded files and directories in \Temp and \Windows\Temp directories. Delete any trash. Now empty the Recycle Bin.

The Windows XP Disk Defragmenter is in Start Menu > Programs > Accessories > System Tools > Disk Defragmenter.

Other Windows have Disk Defragementer in a similar location. If you can't find it, go to Windows Help and search for "defrag" to find out how to run it.

It can take many hours to complete the defragmentation process on large hard disks.

Other more powerful defragmentation utilities are available commercially. The Windows version is quite adequate for most home users.

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Insufficient free Hard Disk space

Open My Computer. Click on View, and enable Details. In the right pane, look at the Free Space available for the partition(s). Concentrate, initially, on the partition (drive) containing the operating system. If the free space is too low then that could be the reason for your computer slowing. Among other matters, Windows and software are forever creating temporary files and these must be accommodated. Also, you must protect against the need to repair, or reinstall, your current Windows and this alone requires considerable free space. Slowing of this nature is usually progressive but could be of sudden onset.

The minimum free space you require is not an exact science. It depends on the operating system installed and also on the type of main PC usage. 100 MB of free space may be fine for Win95, but a full 1 GB is usually too low for Windows XP. Example: on any computer, just writing a full CD may require 600+ MB of hard disk space!

So can you guess how much free space you should have? Open Windows Explorer, right-click the Windows folder, and click Properties. The Size shown is the minimum free space you should have on that drive. If you feel free space may be your problem then try, for testing purposes, to achieve double that figure of free space on the Windows drive. The free space of other drives should never drop below 10% if of a reasonable size.

Every computer, even if used for just a few months, accumulates buckets of unnecessary programs or individual files. These can be removed relatively easily. When uninstalling programs, you may encounter a message asking if you want to remove a shared component - select "no to all" (these files are small and may be necessary for other programs to operate properly).

Create More Free Hard Disk Space:

  • Uninstall unnecessary software. First look for an 'Uninstall' option in that software. Then try Control Panel > Add/Remove Programs.
  • Use Disk Cleanup. This useful utility is installed by all Windows except Win95. Disk Cleanup will delete downloaded program files, temporary Internet files, empty your Recycle Bin and temporary files. Windows XP's version also deletes offline Web pages and compresses rarely used files (you can also remove games, accessories and other non-essential Windows components).
  • Use the freeware Cleanup! utility (for all Windows). CleanUp! is "a powerful and easy-to-use application that removes temporary files created while surfing the web, empties the Recycle Bin, deletes files from your temporary folders and more".
  • Use Search or Find. Find and remove extra large files through Windows' search function. You'll probably find forgotten video or music files. You might also find data files from software/games you no longer use. If you're unsure of the nature of a file, conduct an Internet search using the file name.
  • Empty your Caches. Also limit their maximum sizes.
  • Go to Windows Help and search for "temporary files".
  • Check your E-Mail client. Some users have many thousands of messages in there! Delete the unnecessary.

Leave the Recycle Bin till last if executing manual deletions. Just don't forget to empty Recycled later!

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Insufficient Pagefile (Virtual Memory)

Virtual Memory is the part of a hard disk allocated for use when your operation(s) require more physical memory than is installed on your computer. You can get a slow response if the maximum space available to Virtual Memory is too small for your needs.

This can occur when you have insufficient free hard disk space (see above) or the maximum VM usage has been set too low.

Checking Virtual Memory:

  • Click Start > Help, search for Virtual Memory, and open it.
  • Check the Space Available for the VM drive.
  • Enable Let Windows handle ... if not enabled.
  • Click OK/Apply, exit the VM window, and reboot.

Accessing the VM settings is different on various versions of Windows. That's why using Help is suggested above.

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Memory Problems

Efficient main memory (RAM) and effective memory usage are obviously vital to computer speed. This page concentrates only on items that produce a sudden or progressive slowing. For other memory speed tweaks read Memory Tweaks Centre on this site.

Many memory problems will produce errors of some type but computer slowing may also result.

Resources & Memory Leakage:

If you have plenty of main memory (and Virtual Memory) but your computer gets progressively slower as you use it, then you may be suffering from a lack of resources. This applies mainly to Win9x/Me. In Win9x/Me the resource area of main memory is independent of the total quantity of memory and is of a specific size (only 64 KB in total). Read System Resources on this site for further details.

Every running program uses lots of resources. When closed, the program should release those resources which are then free for re-use. Poorly constructed programs refuse to release all the resources they have used. This is known as memory leakage. Over time, a shortage of resources will result.

There's no specific cure for this apart from running few programs concurrently or rebooting frequently. Your best bet is to use a small utility that frees up some RAM. MemMAX is a small freeware memory optimizer & statistics utility. It was originally developed for the Win95/98 operating systems but seems to also function under Windows Me, NT, 2000 and XP. Create a MemMax shortcut on your Desktop and run it only before opening memory-hungry software like the latest games or cad/graphics tools (and preferably before you receive a memory warning). Freeing about 30% of memory should work for most users but this obviously depends on how much main RAM you have installed.

Get it MemMax 1.1 (freeware, 476 KB) from THPC.

Do you have Faulty RAM?

Main memory (RAM), even if new, can be faulty. Check the integrity of your RAM with the freeware Memtest86 utility version 3.2 for Windows and DOS. Memtest86 creates a bootable floppy disk or CD-ROM. To build the bootable floppy, go the the folder where the files were extracted and click on the Install icon. The created floppy disk will appear to be unformatted by Windows. Memtest86 can be used with any PC regardless of what operating system, if any, is installed.

Get it Memtest86,, freeware, 59 KB from THPC, or visit

Added more RAM recently?

When handling Ram try not to touch the gold connections, as they can be easily damaged. Extra RAM is nearly always a huge performance booster. However, there are circumstances under which adding more RAM actually slows the system (and often causes errors).
• Some proprietary computers do not work correctly if you mix different memory types.
• Mixing, for example, 70-nanosecond (70ns) RAM with 60ns RAM will usually force the computer to run the entire RAM at the slower speed (or perhaps crash the computer). One way around this problem is to enter the BIOS settings and increase the 'Wait State' of the RAM. This can make it more stable.
• Another way to troubleshoot a suspected RAM problem is to rearrange the RAM chips on the motherboard, or take some of them out. Then try to repeat the circumstances that caused the problem.
• Parity error messages refer to RAM. Modern RAM chips are either parity (ECC) or non parity (non-ECC). It's best not to mix the two types, as this can cause of trouble.
• EMM386 error messages refer to memory problems but may not be connected to bad RAM. This may be due to free memory problems often linked to old DOS-based programmes.
• An older system may not have enough cache to handle the additional RAM. If this is your case, the only solution is to upgrade to a new computer or motherboard, as cache cannot be upgraded. This has ceased to be a problem with all newer system.

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Device Conflicts

Any device conflict can cause slowing (and probably other serious problems). Device conflicts are not common on properly constructed systems.

Checking for device conflicts is very easy

Select Start • Settings • Control Panel • System • Device Manager (or a similar path) and click on all the + to open the drop-downs.
First check that all your devices are present - if not, use Add/Remove Hardware in Control Panel to install that item. Now look for:
! a yellow exclamation mark (something is wrong with that device)
X or a red cross (the device is disabled)
beside any device name.
Finding one indicates a problem - most likely cause by a IRQ, or perhaps a memory allocation, conflict.

Correcting a conflict can be problematic

Some devices will only work, or work efficiently, if allocated fairly specific resources, and Windows may have already made this allocation to another device (which could function correctly with different resources).
It is often best, at first, to allow Windows to make its own selection of available resources - you should enable Use automatic settings in all the devices Properties - Resources.

If one device is still not allocated the correct IRQ (or memory area), then disable Use automatic settings for that device, and set it manually using the Settings based on option - Windows will now, hopefully, allocated different resources to the other conflicting device which is still using Use automatic settings. If necessary you can try setting both allocations manually.

Intractable conflicts

The above will correct the most common conflicts such as occur with some video, or sound cards.

Intractable conflicts are not common. However sometimes they can be difficult to alleviate. The ultimate troubleshoot may be to uninstall many of the extra devices (not the hard drive, please!), and reinstall each one according to your own priorities - check the allocation of resources each time, and, if necessary, set the resources manually.

Should you have a serious problem with the allocation of COM Ports (especially with internal modems), then it may be worthwhile uninstalling your entire comm system and reinstall items in a different order until it is correct - you may need the manufacturer's support here.

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Software Conflicts

If a software conflict is causing slowing, you are likely to know the culprit - you've just installed it! The guilty item may not be a full program. It may be an update. Uninstall it and use an alternative if possible.

If you are unsure which is the guilty item, you can restore the system to an earlier restore point prior to when the system slowing began.

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Sometimes overheating of the Central Processing Unit (CPU, or the 'chip') is the cause of computer slowing. Very occasionally it's overheating of other items, like the video card, attached to the motherboard. CPUs are equipped with fans to keep them cool. If the fan fails, or if the CPU gets old, it may start to overheat and you will get bizarre errors. Your motherboard may be smart enough to slow down your processor to protect it but that will slow your entire system.

Ideally, every computer should have a heatsink (it dissipates heat) and a fan for the CPU, plus another fan dedicated to the rest of the items attached to the motherboard, especially the video card. In practice, many computers have just the CPU heatsink plus one fan which mainly cools the CPU - and that setup normally copes quite well!

Your computer's BIOS possibly has a temperature gauge you can use to check for overheating. However, a better method is often to run your computer for some time with the case removed and see if the problem disappears - beware of any physical or electrical damage while your computer is exposed! One remedy is to get a bigger/better fan and install it on top of the CPU, and/or install a second cooling fan.

CPU problems can often be 'fixed' by disabling the CPU internal cache in the BIOS. This will make the machine run more slowly, but it should also be more stable while you consider your options.

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Speed Tweaks Centre >>

• Basics of PC Optimization

• Top 24 Speedup Tweaks #1

• Top 24 Speedup Tweaks #2

= or =

• Cure Sudden or Progressive Computer Slowing

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Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.

Copyright © LarryM 1998-2015