I use Avira because it's free and it performs rootkit scans. Daily nagware is a small price to pay for not opening crap. Also consider a firewall because knowing what traffic goes in or out is important should the antivirus not pick up every new thing. For a better piece of mind, I also change my hosts file to redirect a list of harmful or ad intensive sites to my localhost. The only pain about this is links breaking on a redirect that goes through tracking sites.
Nod32. Haven't had virus in years but you still need to be smart to what not to open. I've also heard Microsoft Security Essentials is pretty good and it's free.
I'm pretty deep into that stuff and multiple experts and magazines say Avira and Kaspersky are the best you can get for free/low money. That's my experience as well, these are the most user-friendly and have the highest rates of detecting viruses.
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Is there an antivirus rating and review site to compare and contrast like for most items for future use and new itmes comes out? Thanks.