I shy away from most reg cleaners because they are notorious for unintentionally corrupting the registry by themselves. Microsoft's reg cleaners are very good at keeping the corruption levels low, but I haven't seen MS release one for Vista yet (I haven't looked to hard yet either though). The only time that I even look into reg cleaning is if I have a known virus that wasn't fixed by my av apps. or a buggy app that did not install with a Windows installer.