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Dual-Boot Win9x + Win9x

Last reviewed: May 2005

Booting to one of two(+) Windows 9x installations on one computer is a huge bonus for many users.

This free utility allow you to dual-boot, or multi-boot, between a number of different, or the same, versions of Windows 9x, all on the same computer.

AddAWins 4.4 page, freeware NEW
Use AddAWins to multi-boot 2 to 6 Windows 9xs.

It function by switching around all boot and boot-related files on root of C:. This utility does not manipulate the boot sector or Master Boot Record (MBR), and does not hide/unhide any drives/partitions.

You can mix FAT & FAT32 Win9xs if C: always uses FAT.

Do not use this utility to install Windows XP, 2K, or any NT.


For the majority of home users, this is a major tweak that even equals overclocking! It's like having a number of computers each with its own Windows 9x. The need to dual-boot will vary considerably between different users.

These are just some reasons for dual-booting or multi-booting:
• You need a 'slim, trim, and beautiful' Win9x, especially for games/music/video
• You need a second (clean) installation of the same Win9x for special use
• You need a standard Win9x plus a 98Lite installation
• You need a 'family' Win9x installation plus your own 'private' Windows
• You need to use WinMe but you have software/games that only run in Win98/95
• You need Win95 for backward compatibility with older software/games
• You need a Win9x for safely testing tweaks, 'trial' programs, shareware, etc
• You need to get away from Profiles on a shared PC - a second Win9x is vastly superior

And so on. The advantages will be clear to you - and they can be very substantial.

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The utilities do not interfere with the MBR (Master Boot Record or Boot Sector)

AddAWins Features:

- Dual-boot, or Multi-boot up to 6 installations of, Windows 9x
- Use all FAT16 partitions or all FAT32 partitions, or use mixed FATs if C: uses FAT16.
- Boot from Windows to Windows (with reboot), or cold boot and use a Boot Menu
- Easy setup & ease of use with Desktop, & Start, shortcuts
- Fast reboot option for individual Windows 9x
- Repair damaged boot files, or restore missing boot files, for each installed Windows 9x
- Remove (& reuse) AddAWins setup for each installed Windows 9x
- Safety features to protect each Windows 9x
- Uninstall AddAWins
- Boot Disk creation, including CD-ROM driver & Repair boot files
- Refresh option for desktop shortcuts
- Show free hard disk space
- History of Windows installations, Repairs, & Removals

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ADDAWINS - More Windows 9xs on the same PC      Windows 9x/Me

AddAWins sets up your PC so you can boot to up to six versions, or installations, of Windows 9x/Me all on the same PC. Most users will find just two, or perhaps three, quite sufficient.

Use AddAWins with any combination of WinMe, Win98SE, Win98, Win95, and 98Lite.
AddAWins makes all of the necessary changes to preserve your existing version(s) of Windows.

Different versions should be installed on different drives - for assured stability.
You can add any retail version of Window 9x/Me in any convenient order.

AddAWins ensures a correct installation if you have an OEM version (read the Error SU0168 on Win9x Install).

There are TWO STEPS to be taken for a new Windows.

1: Bootup with Approved boot disk to run A:\AddStep1
    and install the new Windows (use "Setup /IS" from true MS-DOS).
2: Run AddStep2 (from new Explorer) to complete setup for the new Windows 9x.

You can then use a Wx_WinWx icon to reboot between Windows 9xs.

The README.TXT file is essential reading before you continue.

AddAWins is freeware. You use it at your own risk.

Absolute requirements      Windows 9x/Me

You must comply with ALL the requirements for using AddAWins

1. You must use a FULL installation disk for the next Windows.
    An upgrade disk, alone, can not work.

2. If C: uses FAT16, you can use FAT16 or FAT32 for any other Win9x.
    If C: uses FAT32, you can not install a FAT16 Win95a
    All versions of Win9x use FAT16, called FAT, in the default installation.

3. You MUST USE a different partition for a different Win9x version.
    You can use the same partition only if installing the same version of Windows.

4. You MUST
    (a) create the 'Approved' boot disk (that's for your own protection), and
    (b) make sure your CD-ROM DRIVE WORKS when you bootup with that boot disk.

DO NOT use AddAWins to install a Windows XP, 2K, or any NT

DO NOT use AddAWins with Disk Compression (DriveSpace or DoubleSpace)

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A NEW WIN9x - Using AddAWins to Install another Win9x      Windows 9x/Me

Installing AddAWins
Download addawins44.exe, freeware, 218KB, self-extracting file.
Get a newly formatted floppy disk.
Double-click addawins44.exe to install AddAWins version 4.4 on C:\Addawin.
Let Setup run (it initializes AddAWins, and also creates an 'Approved' boot disk)
or run Setup when ready.

Adding another Windows 9x/Me

1. Click the AddStep1 icon in Start > AddAWins.
   Insert the Approved Boot Disk when requested, and permit the reboot.
   Install the new Windows 9x from true MS-DOS (use Setup /IS).
2. Run Addstep2.bat from the new Explorer AFTER installation.

Booting to another Windows 9x
Use Boot_To > W1_WinXX (icon on Desktop or in Start) to dual-boot to 1st Windows.

Windows labels used by AddAWins
AddAWins allocates W1 to the original Windows 9x, W2 to the second Win, W3 to the third, etc.

OEMs & Message SU0168
Users with installation CDs supplied by OEMs (like Gateway or Dell) would normally receive a SU0168 warning, and the Windows installation would fail. AddAWins overcomes this problem and the Windows will install successfully. Read Error SU0168 on Win9x Install, or Readme.txt in Addawins, for an explanation.

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ABOUT ADDAWINS      Windows 9x/Me

AddAWins is semi-automatic. Once started, you MUST finish it (or run A:\Renew W1).

Your only responsibilities are:
1. to comply with the requirements stated earlier
2. to run A:\AddStep1, then install the new Windows and then run AddStep2.bat.
3. to leave AddAWins files unaltered at all times.

AddAWins protects the boot files of a newly installed Windows.
You will not be allowed:
1. to add another new Windows, or
2. to multi-boot to another Windows until you have run AddStep2 after a new installation.

Restoring original boot files

In the event of any problem, you can run RENEW to restore boot files.
Use Renew_Wx icon (from Desktop),
or A:\Renew W1 (from 'Approved' boot disk in true DOS),
or c:\addawin\renew\renew w1 (from a MS-DOS Prompt, or true MS-DOS)
A reboot will then take you to the original Windows (using an unchanged backup of the boot files for the original Windows). Use renew w2, or renew w3, etc, as appropriate (read renew.txt)

Removing a Windows
Remov_Wx (from Start/Desktop) will remove dual-boot setup for Windows labelled Wx.

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127 GB Partition Limitation in Windows 9x/Me.
Windows 9x/Me must be installed on a partition that starts before 127 GB from the beginning of the hard disk. This physical limitation cannot be avoided.

The order of Windows installation is not important.
You can install the Windows 9xs in any convenient order.

Multiple installations of the same version on the same partition is safe. Installing a different version on a different partition gives assured stability and is considered essential.

Installing different versions on the same drive is not recommended. Some inconsistencies, at a minimum, will occur and some items (like IE) may have a fit!

Remember: The original Windows 95 (& 95A) will not install on a FAT32 system. An error Message SUO 0013 would result, and the installation abort harmlessly.

The Active - Primary - Master Situation
This is already catered for by the installation of the first Windows 9x. The PC system partition is invariably the C: partition and all installed Win9xs boot from there. The Win9x boot partition can then be any logical partition on any hard disk. Do not use more than one Primary per hard disk (Win9x does not like it!).

Message SU0168
This error occurs when an OEM installation CD recognizes an existing Win9x and then refuses to install another. This situation is catered for and you should never receive this message when using AddAWins.
For another possible reason for Message SU0168 read this Microsoft article: Error Message: Your Computer Already Has an Operating System... Q225252].

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THPC has been multi-booting with AddAWins since 1998 without any problems.
Multiple partitions are used on just one hard disk (one PC) or two hard disks (another PC).

All Win9xs, including 98Lite, have been used except Win95b and 95c.

Mixed FAT types is used on one PC (C: uses FAT16), and the other uses FAT32 only.
A mixture of retail and OEM versions, and up to six installations are used.
None of the drives were 'hidden'. Standard Windows partitioning is used.
Linux is also installed on another Hard Disk (hidden from Windows) but that's a separate issue.

It is likely the majority of home users would opt for:
Drive C:   Win9x - the latest Windows 9x - general purpose usage.
Drive D:   Win9x - a slimmed-down, Lite, or older version, Windows 9x - special usage.

THPC has never lost a Windows, not even when developing AddAWins. On two occasions, because of a careless error early in development, it was necessary to rescue with A:\Rescue W1 which saved the situation effortlessly.
However, any Windows' boot files (or AddAWins' batch files) could become corrupt (even if not dual-booting). So protect that Approved boot disk and remember you can run A:\Rescue w1.

Windows Updates & Bug Fixes
All the above Windows were updated without any problems, including Win95 (original).
In recent years none of the updates will install unless the matching Windows 9x version is in use. Nevertheless THPC suggests caution when using updates - make sure you are in the correct Windows version before you install any update - its sensible to play safe.
The reboot required by some updates, or much software/device installation, is not a problem. The same Win9x boots up automatically!

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KNOWN ISSUES      Windows 9x/Me

Partitions: The C: drive may need to be limited in size
The C: partition must start before the 8 GB boundary to be bootable for Win9xs. However, Windows 98+ can boot from beyond the 7.8 GB boundary if your system supports INT13 extensions (this is the norm for many years now).
If using FAT (Win95, 95A), the C: drive must not exceed 2 GB in size.

OEM Win95B & Win95C (OSR 2.x) starting errors with some 'fast' processors.
If you wish to install OEM Win95B or C on a system with one of the following processors,
then you must read this first for a recognized software fix that's required.
  • AMD K6-2 (350MHz or faster)   • Pentium III (1GHz, or faster)   • Pentium 4 (any)
This fix does not apply to retail versions of Windows 95.
This does not apply to Win98, 98SE, or Me which come already fixed.

Win95A may install but not run with fast processors.
The fix (above) does not correct the problem for the retail version of Windows 95.

AddAWins: Automatic Reboot or Shutdown
Some versions of Win95 will not automatically reboot or shutdown when prompted by AddAWins. Users can just press the Space Bar and can ignore the on-screen prompt (or error).

AddAWins: Dual-Boot FROM Windows Me
Users are forced by AddAWins to bootup with the Approved Boot Disk to boot from Win Me to another Win9x. This is a little inconvenient but prevents WinMe from altering your boot files. The Boot Menu Disk is best to use for this - it has no CD drivers and is faster.

AddAWins: Daylight Saving
If you use Daylight Saving then you will need to alter the date at those times of year. Just dual-boot to the other Win9xs and accept the prompt or change the time manually.

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SUGGESTIONS (1)      Windows 9x/Me

Think about items that may affect you in the long term. For instance, if you repartition the C: drive later on, the letters allocated to the other drive(s) will change and you would not be able to boot to another installed Windows 9x! Make a plan before starting. Get any repartitioning out of the way BEFORE starting.

Disk Check
Lingering disk errors can cause horrible problems. Run Scandisk's Surface Scan on any target drive before installing there.

Program Files
Some older software will not run on Win98(+) systems. Its best to make clear which Win 9x installs which software. User should avoid using Program Files as the installation directory.
You can create new folders on the root of any drive used for installing software and install into each folder as appropriate e.g. C:\ProgsSE, or E:\Prog98_2 and E:\Progs95, or . . .
You can, of course, install a program anywhere you like (but make life easy for you and Wins, especially for uninstalling!)

Virtual Memory (Swap file):
Making all the Windows share the same Swap File (Win386.swp in the Windows directory by default) can save some Hard Disk storage space. Use a PERMANENT Virtual Memory, IDENTICAL in ALL Windows, and point them ALL to the SAME LOCATION. Be generous with its size - large enough to satisfy the greatest need of any Windows, plus a little extra for future needs. Delete the old Win386.swp files.

Shared Programs
16-bit programs: These can be normally be run from any Windows 9x.
32-bit programs: Reinstall 32-bit software for use with that particular Windows 9x.
It's tempting to (and we will) install it over a previous installation to save on Hard Disk space. This works in MOST cases. However, there will be problems if there are discrete versions of required .DLLs for Win98/SE/Me/95. THPC does not have further information on this, and prefers to use each Windows as separate entity (just like having X number of Windows computers that just happen to use the same hardware).

Its all very well having a splash screen when Win 9x is loading. However you can easily lose track of which Windows is loaded when you have been working for some time.
This is easily overcome by giving each Windows a very distinctive appearance.

Keep these in mind:
1. Install the new Win into a distinctive folder like Win98, or Win95, or WinSE_2 (not 'Windows')
2. Leave the first Windows at its default appearance.
3. Give the other Windows 9x its own distinctive color scheme. In the new Windows, right-click an empty area of the Desktop and select Properties, then the Appearance tab. Now select a Scheme and/or a Desktop color, and use a variation of that color for the other items. Experiment to suit yourself.
Keep it readable!

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WHY DUAL- and MULTI-BOOTING WORKS      Windows 9x/Me

Every Windows will boot from the C: drive, and use the boot files currently on the root of C:. Those boot files then determine which Windows 9x to use and the location of that Windows 9x.

The Boot Files : The only items that need be changed are the boot files for each version of Windows 9x. These are IO.SYS, MSDOS.SYS, COMMAND.COM and, if used, AUTOEXEC.BAT and CONFIG.SYS. The disk compression files, DRVSPACE.BIN and DBLSPACE.BIN could also be involved but THPC recommends that you DO NOT dual or multi-boot if using Disk Compression. The splash screen (LOGO.SYS) can also be included for clarity on the version loading.

Boot files contain information specific to each Windows 9x installation, including the disk location of (the boot path to) that Windows 9x. Merely switching these boot files to those of another Windows 9x will cause the other Windows to be loaded during the next reboot.

The Boot Sector & Master Boot Record : When the hard disk was FDisked/Formatted, all versions of Windows 9x/Me created a boot sector and MBR (Master Boot Record) on the hard disk. They all use the MS-DOS component of Windows to create the MBR. Therefore all version of MS-DOS (later than version 5) create a boot sector similar to that of the others. So all versions of Windows 9x/Me can use the same MBR. We only need to change those boot files.
But what about the FAT type?

The FAT type : Be CAREFUL here. The C: partition can use FAT16 or FAT32 but the C: partition will ALWAYS have to use FAT16 if mixing FAT16 and FAT32 Windows9xs on the same computer (if Windows 95, 95a, is ever to be used). Only Win95b/c (OSR2) can use FAT32, as can Win98 and later.

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The download file contains all the information given on this page.
Please read the enclosed Readme.txt file BEFORE you use AddAWins.
Download AddAWins (ver 4.4, freeware)

Click HERE to go to the AddAWins download page.
Click HERE to download the AddAWins Readme file (, 11 KB).

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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.

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