For a complete and simple 'maintenance' of the system try running the free scans from Microsoft
Doing the complete thing will take a long time (since it does do the defragmenting, malware scans, etc as well)
Click Complete Scan and follow directions, once scans start, go make lunch or something and come back to check once in a while if it needs anything.
http://onecare.live.com/site/en-us/default.htm
Astrophel at capitaltechmd.com, February 2009