AdAware

http://lavasoft.com/products/ad_aware_free.php
download at bottom of page What is Spyware and Adware? Adware and Spyware is software made by people designed to interfere with your computing experience. If you experience popups, slow internet speeds, or other kinds of PC interruption, chances are you are infected by some of these files. That is why we designed our revolutionary product.Why does Spyware and Adware affect every internet user?Your personal information can be collected and shared with third partiesUnauthorized icons can appear on your desktopUnauthorized sites can add themselves to your internet favoritesYour browsing activity can be tracked and monitoredUnwanted toolbars and searchbars can attach themselves to your browser without your knowledge or approvalYour personal information can be intercepted when you enter it onlineYour default homepage and settings can be hijacked so you can't change themThese malicious components not only invade your PC so they can not be removed, but take up your hard drive space and slow down your PC!