SovietCommissar

I've always used CCleaner, but I've found that registry cleaners are somewhat dependent on who's using them - to a degree, and if you look around the internet you'll find some backup in that registry cleaners are not the end-all of system problems like their makers often purport. Therefore my main motivation for using CCleaner is that it's also an uninstall launcher and cleans up temporary files and so on.

@ Brink -

I've heard a lot about Wise, I guess I'll look that up and give it a try.