FWIW, I ran RegClean (many months ago) on my NT 4.0 machine which was promptly hosed. Had to resort to my emergency repair disk. Was informed by coworker that, well, he questioned my intelligence for running RegClean on NT. So, you might want to beware (?).

>Over a period of time the registry may begin to contain corrupted, unused and/or unnecessary keys. RegClean is a program designed to remove these.
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>Go to the Microsoft site and search for Knowledge Base article Q147769. It contains information on using the program, as well as a link to download it.