When you attempt to remove Plus! you receive a message similar to:

1635 This patch package could not be opened. Verify that the patch package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer patch package.

You have a corrupt registry key.

to fix the problem:

01. Use the Registry Editor to delete the following key:

HKEY_LOCAL_MACHINE\Software\Classes\Installer\Products\DFAD2CEE8555CA04E8C905508C8F018E

02. Start / Control Panel / Add or Remove Programs.

03. Select Microsoft Plus! for Windows XP and press Remove.

04. When prompted, press Yes to confirm.

05. Shutdown and restart Windows XP.

06. To re-install Plus!, insert the Plus! for Windows XP CD-ROM, holding down the SHIFT key to prevent it from auto-starting.

07. Start / Control Panel / Add or Remove Programs.

08. Press Add New Programs, in the left-hand pane.

09. In the right-hand pane, press CD or Floppy.

10. Follow the on-screen instructs to complete the installation.