Everyone has heard of TuneUp Utilities, there is no need to introduce it. All I want to say is that everyone can get TuneUp Utilities 2010 (TuneUp Utilities 2011 costs $49.95, or $24.95 if you install it then uninstall it while it is in trial) for free!
Promotion/registration page: http://www.tuneup-software.co.uk/promo/cs0411/ 
Download link: http://download.tune-up.com/TUU2010/TU2010TrialEN-GB.exe 
Product page: http://www.tune-up.com/products/tuneup-utilities/