The Register Cleaner program by Jouni Vuouro has worked great for me on my WIN2000Pro system. It will among other functions go through the registry and list non-valid items. Just the ticket for when things go astray and you need a little help. Go to the web site and read about it.
www.vtoy.fi/jv16/ I hope I am right on the web page. It does support 2000,xp,98 but has a note about win95 so read his writeup.