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Create a new BOOTSECT.DOSReviewed: April 2005BTSECT creates Bootsect.dos if it's missing, incorrect, or corrupt.A Windows cannot boot without its OS Boot Sector. This is a small bit of code at the start of the system partition (that's the Primary partition marked Active and it's also where all the bootfiles must reside). The sector's code is OS-specific because it points to a specific bootfile (NTLDR for a NT-type OS, or Io.sys for a Win9x/Me-type OS).In a dual-boot of a Windows XP/200/NT with a Win9x/Me, the XP/2000/NT OS Boot Sector is still at the start of the system partition, while the OS Boot Sector for Win9x is stored in C:\Bootsect.dos. When XP/2K/NT is selected from the Boot Loader Menu, the XP/2K/NT Boot Sector is used in the normal manner and uses NTLDR. When, and only when, Win9x is selected, the OS Boot Sector held in Bootsect.dos is used (instead of the XP/2K/NT sector) and uses Io.sys. Please read Boot Sequence in a Windows Dual-Boot Explained if you require more information on this topic. This page shows how to create a new Bootsect.dos 1. when Bootsect.dos is missing or corrupt, or 2. when setting up a dual-boot even if the current OS Boot Sector on the system partition belongs to XP/2K/NT. The utility used is THPC's Btsect25.zip (freeware). The download contains Btsect.bat and Bootread.scr (and a text file) which run in true MS-DOS from your Win9x/Me Startup Disk, or from an ordinary Win9x/Me boot disk. • If using a Win98(+) Startup Disk, Choice.com MUST be added to that floppy. • If using an ordinary Win9x boot disk, you MUST ensure that floppy contains: Attrib.exe, Choice.com, Debug.exe, Sys.com (same Win9x/Me versions). [top of page] What Btsect.bat does
[top of page] How to Use Btsect.bat
Example: COPY C:\WINDOWS\COMMAND\CHOICE.COM A:\ Note: If, and only if, you are stuck, you can try using any Win9x boot disk. However, the extra files added to that boot disk must be the same versions as the rest of the files on that boot disk. Mixing different versions does not work and should not be tried. [top of page] Btsect.bat ExplainedIn a Win9x + XP/2K/NT dual-boot, the first Primary (bootable, system) partition of the first hard disk always contains a XP/2K/NT Boot Sector. This first Primary is almost always the C: partition and its XP/2K/NT Boot Sector controls the initial part of boot up in this dual-boot. This will be true even if the Windows directories are installed elsewhere e.g. Win9x in D:\Windows and XP/2K/NT in E:\Winnt - boot control will still be from the first Primary (C:).If Win9x is selected from the Boot Loader menu, Windows XP/2K/NT executes Bootsect.dos, simulating the Win9x system's normal boot procedure. Btsect.bat uses the DOS Debug command to create an image of the current OS Boot Sector of the C: drive. That image is saved to c:\Bootsect.dos. Btsect.bat runs only from true/real MS-DOS. Note: Btsect saves the OS Boot Sector (512 bytes) irrespective of which OS created it. Btsect.bat first backs up any Win9x or XP/2K/NT boot files it finds in root of C:. An existing Bootsect.DOS is saved as Bootsect.PRV Use this utility only if C: is the PC system partition for a Windows 9x/Me (Win9x boots) or only if you are prepared to create one here (using the SYS C: command). If using a third-party boot utility you should use its own Options. If you currently have a Win9x Boot Sector (Win9x boots normally) then Btsect.bat will create a valid Win9x image of it in Bootsect.DOS However, it is quite likely that you have a OS Boot Sector for XP/2K/NT, or the OS Boot Sector is corrupt. In these cases you should use the SYS Option from within Btsect.bat to first create a new Win9x Boot Sector on C:. A valid Bootsect.DOS is then created. In all cases, when Btsect.bat has been run: Win9x will be bootable Win XP/2000/NT will not be bootable until its own OS Boot Sector has been restored. Fortunately XP/2000/NT CD or Setup Disks cope with this quite reliably. The download contains a text file with full instructions. [top of page] OS Boot SectorIt must be emphasized that it is the current OS Boot Sector of the first Primary partition (C:) that is copied. Therefore you must ensure that the current OS Boot Sector of C: is valid for Win9x, is not damager, and is not for the XP/2K/NT. Otherwise you would only create an image of a faulty, or a XP/2K/NT, OS Boot Sector.If the PC boots naturally to Win9x, and not to XP/2K/NT, then C: is likely to be a valid Win9x Boot Sector. However, do not rush to use the Sys option. Depending on circumstances your dual-boot 'may' be OK. If you can not dual-boot, you should first check the timeout= line in Boot.ini just in case you find it set to 0 AND the Default is set to Win9x. If that were the case then the OS Boot Sector could still be for XP/2K/NT but you never see the boot loader menu. If Timeout is 0 then set it to 15 and reboot (that 15 represents 15 seconds). [top of page] How to Edit Boot.iniThe Default OS and the Timeout settings are in Boot.ini.Boot.ini can be edited from DOS or via the Control Panel. Be careful of typing errors if modifying Boot.ini because doing so may make your computer unusable. From Control Panel:
[top of page] SYS CommandYou don't need to use the SYS option if the current OS Boot Sector is for Win9x/Me.Note: All versions of Win9x can boot from the same Win9x Boot Sector! But . . . Note: All versions of Win9x must have their own system-specific boot files on C:\ ! SYS C: creates a new Win9x Boot Sector on C: (it will work with ALL Win9xs irrespective of the Win9x version creating it). It overwrites the current OS Boot Sector (which may be for Win XP/2000/NT but that can/must be repaired later). BUT SYS also copies Win9x system-specific boot files from A: to C:. The Win9x that made the Startup disk will be shown by Btsect.bat. It should match the Win9x installed. Using the correct version of Startup disk is important. An incorrect version of Startup disk will copy incorrect system boot files to C: ! Also Note: If a Win9x version of Msdos.sys does not already exist on the C: drive, then the Sys C: command will copy the version from the floppy over to C:. This floppy version is nearly empty (it's a dummy) and it will not boot your Win9x. Digression: [top of page] Repair XP/2K/NTYou can read about repairing a Windows XP/200/NT on the Repair a Dual-Boot page.As you will have realised, a valid Win9x Bootsect.DOS can only be created when a Win9x Boot Sector exists. This inevitably means the XP/2K/NT Boot Sector must always be repaired after Bootsect.DOS has been created. This applies whether or not you have to use the SYS command. Fully research repairing the XP/2000/NT Boot Sector before you start. Always backup Bootsect.dos, and all other boot files, before you execute a Repair. In general, you boot up with the XP/2000/NT CD or Setup Disks, enter the Recovery Console, and run FIXBOOT at the prompt (use Inspect Boot Sector for NT). Running the repair is easier if you have made the XP/2K/NT Rescue Boot Disk as recommended by THPC. Now Windows XP/2000/NT will boot again, and you should also be able to dual-boot to the Win9x. The dual-boot function sometimes needs a little help: [top of page] BOOTSSSome NT 4 users may encounter an error suggesting that Bootss is missing or corrupt. This is itself a wee bug! It is Bootsect.dos that is missing.The Ntldr file displays the erroneous file name Bootss instead of the correct file name of Bootsect.dos. Microsoft has confirmed this Bootss error to be a problem in Windows NT version 4.0. [top of page] What Microsoft says on "Reconstructing BOOTSECT.DOS"Microsoft says, when referring to Windows NT 3.1-4.0 (Microsoft Knowledge Base Article - 101789):Bootsect.dos is created by Windows NT Setup. The OS Boot Sector found in sector 0 of drive C is copied into Bootsect.dos before Setup writes the Windows NT boot sector. (Setup will not overwrite an existing Bootsect.dos.) If you choose a previous operating system, Windows NT executes Bootsect.dos, simulating the previous operating system's normal boot procedure. Because the information in Bootsect.dos is really created by the previous operating system, it is very difficult to re-create. You must transfer the BIOS parameter block (BPB) from the boot drive (C) at sector 0 into the boot code from the previous operating system and write this into Bootsect.dos. To do this, use the following procedure:
Note that MS says "Setup will not overwrite an existing Bootsect.dos". It appears a repair of XP/2K/NT does not always produce the required Bootsect.dos. THPC suggests you should always create it yourself if/when you can! [top of page] Dual-Boot Centre [top of page] * ALWAYS BACKUP FIRST * ALWAYS RECORD SETTINGS * ALWAYS MAKE ONE CHANGE AT A TIME TweakHomePC is at: www.thpc.info Copyright © LarryM 1998-2007 thpc@mail.com |
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