I'm a volunteer with the AARP free income tax preparation service, and we changed our anti-virus
software this year. AARP Tax-Aide is a nationwide program, and AARP used AVG until this year. AARP is recommending Microsoft Security Essentials(MSE), a free download from Microsoft that is simple to install,and runs in the background.
Our State (Alabama) technical guru switched from AVG to MSE and MSE found two viruses that AVG hadn't detected. It's very easy to install.