CCleaner and HijackThis
Cnet recommends a free tool called CCleaner that is supposed to have a registry cleaner as part of it. They also list HijackThis as a good tool to look for spyware on your windows machine if you are having specific problems. I've heard of that one before, but wasn't sure if it was legit. Seems so. Mainly, I'm posting these here so I can find them again later.