Registry cleaner that works
I've been using Winaso on my Vista and XP machines for the last 3 or 4 years. Finds quite a few entries and never had a problem deleting anything important. I like Advanced System care too, both are quite a bit better than CCleaner which I also use, it never seems to find much though.
I like using Registry cleaners, along with Revo uninstaller, keeps my PC from getting too bloated, system always seems as smappy as day 1. I have tried some that have caused problems though, most of them I wouldn't trust.