I personally find that Avira and Avast are good. AVG used to be good but the newer version seems to consume more CPU resources than the v7.5 (You won't see it as much of an issue if you run it on PC with spec higher than P4 3.2GHz with Minimum 1GB of RAM).
Avira is so far (I find), the best for getting rid of trojan, but you can only get the updates slightly later than the paid version (Well at least its free). Avast has this command-line bootup scanning feature that allows removal of viruses and spyware easier (Can allow removal of spywares or trojans that are running in the background when your window start).
Well thats my opinion for the FREE Antivirus.
Avira is so far (I find), the best for getting rid of trojan, but you can only get the updates slightly later than the paid version (Well at least its free). Avast has this command-line bootup scanning feature that allows removal of viruses and spyware easier (Can allow removal of spywares or trojans that are running in the background when your window start).
Well thats my opinion for the FREE Antivirus.