The suggestion I have gotten from major computer people is to use the following 3 products:

1) Ad Aware
2) Spybot S&D
3) Google Toolbar

Google toolbar is good at stoping popups, ad aware removes things that spybot does not get, and spybot removed things that ad aware does not get.

Plus you have to be carefull where you get ad aware since there are some "fake" ad aware programs with the same name... but I have not looked too much into that.