Registry problems can be a pain in the proverbial. One solution I have used in the past is to restore my registry to a date when I knew that everything was OK, then start again with a clean sheet.
If you are running Windows me, look in accessories/system tools/system restore and restore your system to an appropriate date. For earlier versions of windows, restart your pc in dos mode and at the C prompt type scanreg/restore. You will then be presented with a selection of dates to restore your registry to. This has worked for me on the many occasions I have screwed up, but someone out there with a bit more knowledge may have a better idea.