i would redecomend the Avast Anti virus free your get to keep it forever and all you have to do is register and i have active protection ive used it for a couple of years and i have blocked every virus that has tried to get on
I use Comodo Internet Security and i am happy with it.It doesnt uses a lot of resources, it has a firewall and a high detection rate.It also has a sandbox and pretty strong HIPS. It has a program called kill switch (more information about it here: http://help.comodo.com/topic-119-1-328-3518-.html ) its smilar to task manager.It also has a virtual kiosk (more information about it here: http://help.comodo.com/topic-72-1-451-4738-The--Virtual... ).It also has a gaming mode.You can also make a rescue disk with it.And i think it is the best free AV.