My computer guy also recommends AVG, he had my dad install it on all of the computers at his work a few years ago, and they never had a problem at all. I had issues with Norton using up my memory in the background, and at the time I barely had any RAM to start with LOL.
I did buy the AVG for my new laptop, I'm protecting that baby LOL. I do have the free version on my desktop and used it for years now without problems.