Dual-boot considerations

Dual-boot considerations

From Inside Windows 2000 Server by William Boswell, New Riders, 2000.

Bootstrap loader limitations. The Windows 2000 bootstrap loader, NTLDR, can load any version of NT or Windows 2000 from any drive or partition on the local system (except some flavors of removable media drive), but it can load only one alternate operating system. It does so by storing the boot sector for the alternate OS in a file called BOOTSECT.DOS at the root of the boot partition. If the alternate OS is selected from the Windows 2000 BOOT menu, NTLDR shifts the processor back to Real mode, loads the image from BOOTSECT.DOS into memory at 0x700h just as if it had been loaded by a standard INT13 call, and then turns control over to the executable code in the image.

Booting Two Alternate Operating Systems with NTLDR

If you need to boot more than two operating systems and one of them is not a Windows OS, use a partition manager, such as Partition Magic, System Commander, or Linux Loader (LILO).

If you want to configure a triple-boot machine to load DOS/Windows, Windows 9x, and Windows 2000, you can create a triple-boot menu with two alternate BOOTSECT files by layering your installations. This process is described in detail in Microsoft's KnowledgeBase article Q157992. The basic steps are as follows.

Booting Two Alternate Operating Systems

  1. Install DOS.
  2. Install Windows 2000. This saves the DOS boot sector to BOOTSECT.DOS.
  3. Toggle the read-only, hidden, and system attributes on BOOTSECT.DOS.
  4. Rename BOOTSECT.DOS to BOOTSECT.622, for DOS version 6.22.
  5. Install Windows 9x. This overwrites the Windows 2000 boot sector with its own boot sector.
  6. Run the Windows 2000 Repair Console. Use it to restore a Windows 2000 boot sector, and save the existing boot sector as BOOTSECT.DOS.
  7. Toggle the read-only attribute on BOOT.INI.
  8. Edit BOOT.INI to add the following lines:
       
        
                   [Operating Systems]
                          c:bootsect.622="DOS"  /win95dos
                          c:bootsect.dos="Win9x" /win95
    
       
    The switches enable multiple boot features in Windows 9x.

For more information about Inside Windows 2000 Server go to New Riders.

This was first published in July 2000

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