Why do I receive the error message "Setup can not uninstall Windows XP because the necessary registration information is missing" when I try to uninstall XP?

A. You might encounter this error message when you attempt to use the c:\windows\system32\osuninst.exe command and either of the following conditions exists on your computer:

  • The Undo folder isn't present on the system.
  • The Win9xundodirpath and Win9xundointegrityinfo registry values are not present in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup registry subkey.

The Undo folder is typically located at the root of the C: drive and contains hidden and system attributes. To view the folder from the recovery console or command prompt, you need to type

dir /ahs
or set the folder permissions by typing
attrib -sh c:\undo
If the folder is missing, you can't uninstall the OS.

If the registry information is missing, try restoring a previous registry backup. Again, if this information is missing, you won't be able to uninstall the OS.

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