Many administrators share a curiosity bug. There are useful tools in Windows NT \support folder of the installation CD. There is also ROLLBACK.EXE. Rollback is a developers tool. It was designed to purge the registry of any information added since the GUI phase of installation. You know, install Windows NT, add an application or two, test, rollback. Try it again. Guess what it does to your NT with its many applications installed? Useful utility with deadly consequences which should have been label "dynamite : at your own risk".

It seems that history repeats itself, but now the "rollback" utility is being preinstalled by OEMs. See Microsoft KB article Q312369 You May Lose Data or Program Settings After Reinstalling, Repairing, or Upgrading Windows XP due to the system32\Undo_guimode.txt file.