CCleaner is one of the best PC Cleaners available it removes those unused files that build up over time, gets rid of bad links, useless dll files.  Just download it, run it, and watch what it cleans up, best of all this one is free for download and personal use.  This one can also help clean up your registry.

From CCleaner :  CCleaner is a freeware system optimization, privacy and cleaning tool. It removes unused files from your system - allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. Additionally it contains a fully featured registry cleaner. But the best part is that it's fast (normally taking less than a second to run) and contains NO Spyware or Adware! To download CCleaner click the blue arrow below.