I periodically sweep my system for spyware using Lavasoft's shareware program Ad-Aware (www.lavasoft.de I believe).
It helps keep my performance speed up and surfing untracked.
Try Spybot. Spybot is definitely the new king in spyware and adware removal. I have tried it for a while now and it is more comprehensive, thorough, and faster than ad-aware. Ad-aware still has a great following and great guys working to make it number one, but in my opinion Spybot currently holds that honor. It's free too.
http://www.surferbeware.com/free-downloads.htm