I have been using Avast anti virus for a few years now and highly recommend it. It's better than a few I have paid for like norton, mac fee etc.. It's caught all the virus I have thrown at it. I have tested it by downloading files I knew contained viruses and it caught them all like a trooper...it also stops attacks from web pages by disconnecting before it has a chance to attack..overall I'd say it's one of the best I have ever used and it is also light on resources and doesn't bog your system down like Mcafee does. Give it a whirl you won't regret it. But if your ultra paranoid like me don't trust windows altogether and dual boot a Linux distro.. I do all my Internet shopping and banking on Linux and the majority of web browsing and mainly use windows for gaming as not all games are compatible through wine on Linux.