Download and install TuneUp Utilities 2011 its not free but there is a 15 day trial demo, run Tuneup and let it fix all the problems it finds. Its a good app, that monitors everything & tells you what needs correcting, solved a registry problem I couldn't fix one time there. Even has a gaming mode you can setup where it will disable programs that run silently in the background so you get more gaming power!. Tuneup has been around for 15yrs so its not some newbie app trying to break into the market.
http://www.tune-up.com/download/