I'd like to add another + 1 for MS Security Essentials. I don't want to get into a long winded statement but I've used, Norton, McAffee, Fprot, Adaware, Spybot, Malwarebytes, AVG, and thats just what I can remember off the top of my head... LOL
MS Security Essentials has been the best so far. It protects your computer. Take very little resources. Doesn't interfere with the music software..
What more can you ask?