Hi, acme.
Personally, I do not recommend "tune up" tools or registry cleaners. Windows is a closed source system. Developers of registry cleaners do not have the core code of Windows 7 and are not working on definitive information, but rather they are going on past knowledge and experience. Automatic cleaners will usually have to do some guesswork.
Modifying registry keys incorrectly can cause Windows instability, or make Windows unbootable. No registry cleaner is completely safe and the potential is ever present to cause more problems than they claim to fix.
Registry cleaners cannot distinguish between good and bad. If you run a registry cleaner, it will delete all those keys which are obsolete and sitting idle; but in reality...