Glocksoft has a really nice one - this one you need to be careful with, it will pull out a LOT of stuff that needs to stay put, but if you know what to look for it lets you delete individual keys and saves everything in a nice browsable tree format similar to regedit. You can get it here:
I really like that one from Glocksoft. The features in it are unmatched by what i've tried to date. It's backup function is impeccable. I actually ran Regclean after running the AATools version and it pulled out a ton more stuff, but because it's not rated for XP (and development is stopped on it now), I slapped everything back in likity split.
I just went back to the glocksoft site and noticed they also have a forum. AATools is rated for Windows 9x/Me/NT4/2000. I'll ask them if there are any known issues with XP and post back when they answer. They also have a beta testing program for anyone who would like to get in on that level of development with them (cool ).
AATools is actually a whole suite of programs. Their description: AATools is a multithreaded network diagnostic tool. Its purpose is to accumulate data pertaining to network status and availability, using all of the latest development tools in network research. It is a 11-in-1 utility, including TCP/UDP Security Port Scanner, Proxy Analyzer, CGI Analyzer, Email Verifier, Links Analyzer, Network Status, Process Info, Whois, System Info, Resource Viewer and Registry Cleaner.
It's shareware but worth a look-see in my opinion.
I can second that. It goes through all 5 hives, and is very thorough from what I can tell.
And if anything it errs on the cautious side, which is good. No worry on deleting things that shouldn't be deleted.