Windows Live OneCare
OneCare from Microsoft is pretty awesome. $49 dollars a year for three PCs that gives you protection from spyware / viruses, system cleanups and tune ups in the way of auto defragmentation and registry scans. It does cost money but once a month I head over to their free safety scanner (must be ran using IE6 or IE7) and download the FREE tool which does almost everything that the full suite does. The only difference is the $49 dollar package is always performing this tasks and the safety scanner only runs a scan when you go to the site. For monthly tuneups, this is a great tool!
Check it out.
