Read here :
http://anti-virus-software-review.toptenreviews.com/
http://jaxov.com/2009/05/top-10-antivirus-programs-2010/
http://www.all-internet-security.com/top_10_antivirus_software.html
i'm using free antivirus:
http://www.avast.com/free-antivirus-download
so far..so good!