I highly endorse ad-aware to remove spyware and other unwanted leaches.

For elliminating unwanted pop-up windows all together, I highly endorse EMS Free Surfer MKII:

http://www.webattack.com/download/dlfreesurfer.shtml

Both of these softwares have received 100% positive reviews.

If you use kazaa, there are several tricks to remove the spyware but maintain functionality. Check out the following for how to do so: http://www.geocities.com/little_kingston77/