"Internet Security" from company called "Trend Micro" is the best. I have used it on several machines and that damn thing keeps the machines clean from viruses, adwares, spywares etc.
They sell it in Best Buy and Circuit city as well as online from their web site www.trendmicro.com. You go to Best Buy's web page for software and you will see that Trend Micro is in their featured brands.
http://www.bestbuy.com/site/olspage....&type=category

It is like $50 but has 3 licenses to be installed on 3 PCs. It also comes with free support by phone.