Have you tried CCleaner? It has a pretty good registry cleaner that allows you to make backups in case you remove something that you shouldn't have. It's free so there isn't a trial period or nag screen and it's virus and spyware free too. I'd recommend the slim version as it doesn't include the Yahoo or Google toolbar (can't remember which one comes with the standard version) but does everything else the standard version does. You can get it here:
http://www.ccleaner.com/download/builds.