Ad Aware by Lavasoft is free and reliable. IT gets ride of spybots and all that garbage effectively.
To prevent pop ups ENTIRELY, I use the Mozilla web browswer. Netscape is descended form it, and it hgas far superior security features and capabilities than Microsoft could eVER hope to accomplish. I especially LOVE the cookie management whihc no one else does so effectively.
Ok, it blocks programs from popping up windows, you can block websites from eVER siending you advertisements or cookies (LOVE the graphics block, imagine never having to see banner ads on any web page again!
BNest of all, its free.
<a href="http://www.mozilla.org" target="_blank">www.mozilla.org</a>