The free version of AVG (AVG Free) is fully functional. The only real differences with the payware version is that you you can't schedule things as precisely (you can only schedule automatic updates and/or full system scans to happen once a day, and the free version doesn't include the firewall.
(The free version is a bit hidden away on their site since they hope people will spring for the payware one, of course)
(The free version is a bit hidden away on their site since they hope people will spring for the payware one, of course)