RegSeeker
Hey will ya look at that. Regseeker actually made my computer a little faster. I had it remove a few thousand unused registry entries and my Windows XP computer got a little faster. I was a bit worried that it would do Very Bad Things to my registry. I made backups and stuff. It’s been a week and so far, no earth-shattering “kaboom” like that accident with the space modulator.
It’s freeware available in many places, including locally.