Excuse me, but that is flat-out incorrect. AVG, Avira, and Avast all offer protection on the same level as the most common for-pay antivirus programs (McAfee and Norton)—the actual rankings will leapfrog around over time, but they all detect and repair damage from so close to 100% of viruses that it makes little difference which one you use (McAfee's currently in a bit of a slump, though). You have to remember that a lot of the free programs are loss leaders for companies that also sell antivirus products aimed at business—the business software may have additional features, but in general both versions will use the same set of virus definitions.