JSI Tip 2318. You can't upgrade W9x to Windows 2000 if you dual boot with Windows NT / Windows 2000.

If you are dual booting W9x with Windows NT or Windows 2000, you will receive:

       	Windows 2000 Setup does not support upgrading from Windows if you have multiple operating systems
        installed. Setup will now exit.

        or

         Other Operating Systems Found

        You cannot upgrade this Windows installation to Windows 2000, because you have more than one operating
        system installed on your computer. Upgrading one operating system can cause problems with files shared by
        the other operating system, and is therefore not permitted.

when you try to upgrade.

Microsoft does not support upgrading W9x when Windows NT and/or Windows 2000 is detected, as the upgrade is likely to overwrite common files.

To upgrade W9x, you must:

1. Remove the Windows NT and/or Windows 2000 folder.

2. Delete c:\ntdlr, c:\Ntdetect.com, and c:\boot.ini.

3. If you were dual booting with Windows 2000, delete the C:\Program Files\Uninstall folder.