Are you getting Error 1327. Invalid Drive: E:\ or F:\ or G:\ using Windows XP SR2 when using Microsoft Automatic update or Windows update?
This actually happened to us when we had to perform data recovery on our main C:\ drive in Xp. We reassigned our F:\ drive to D:\ and in the process forgot that some of our Microsoft Office Professional Edition 2003 program files had been installed on the old drive letter F:\ drive!
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. We cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
Edit a registry key. Click Start then Run then type regedit and navigate to:
Change LocalCacheDrive to a valid drive letter like C.
Have a good backup before you attempt this!