i agree with every1 that says avast. its the best free one out there.. be careful with free ones though. sometimes they install virus onto your comptuer to make you pay for the full version.
I second AVG but a couple of really annoying malware programmes have gotten through it recently after downloading films off the net and I had to usemalware bites and another pc etc to fix it... Still I don't think any other antivirus would have prevented it either.
I generally use Norton but a good free one is MalwareBytes Anti-Malware. Sometimes its found items that Norton missed.
I use AVG. I have for a long time, and never had problems at all. I never had viruses, etc on my computer.
all antivirus is the best but the more important is our carefully is using an internet and storage drive
I use Microsoft security essentials for two years and no problems till now. It is free and totally secured.