When it comes to registry and hard drive cleaning, Crap Cleaner is pretty much the standard program of choice:
http://www.ccleaner.com/It's free and it does things better than other commerical programs.
I also like Tweak Now's RegCleaner.
It has a free and a pay version. You can pick it up here.
http://www.tweaknow.com/RegCleaner.html