IMPORTANT: The procedure to manually uninstall Windows XP may cause data loss. It is recommended that you backup all your data before you proceed. In case you cannot start Windows XP, use a 98 or ME bootable disk to access your data.
Once you are able to access your hard disk, look for folder named UNDO in the system partition, where you installed Windows XP. If you find the folder, look for the cab file named boot.cab. You will have to use the command line to uninstall Windows XP in this case. To open the command prompt, click Start, RUN, and type CMD in the RUN box.
In the Command Prompt Window, type in the following:
[1] CD\
This command takes you to the root folder of the system partition. \ represents the root folder.
[2] EXTRACT c:\undo\boot.cab /e /y
This command extracts the files copied by Windows Installer into boot.cab while upgrading to Windows XP (for rollback).
[3] copy c:\$win_nt$.~bt\txtsetup.sif
The command copies the SIF file containing information about Windows upgrade to the root directory.
[4] copy c:\$win_nt$.~bt\bootini.bak
The command copies boot.ini containing information about "Windows 9x boot parameters" to the root directory.
[5] attrib -r -s -h boot.ini
Removes all attributes - hidden, read-only, and system attributes - from "boot.ini" so that it can be modified using following commands.
[6] ren boot.ini boot.xx
Renames current (Windows XP) boot configuration to a different filename
[7] copy bootini.bak boot.ini
Copies original Windows 9x boot file backup to "active boot file" so that you boot with your Windows 9x boot settings.
[8] Reboot the computer. On the boot menu, select Cancel Windows XP Setup and proceed to check if you previous OS needs any repairs. You may have to reinstall some programs once you are on your Windows 9x operating system.
Though a little bit tough, this is the best method to manually uninstall Windows XP from your computer.
NOTE: If you are not able to find the folder UNDO, it is recommended that you backup all your important data and perform a clean reinstall of your Windows 9x or Win Me instead of trying to uninstall Windows XP.