You just described my computer’s performance as of late and now I know why. What anti-virus program do you recommend now?
Being that I am primarily a Mac user, I should issue the obligatory "Get a Mac!" comment—but I shall refrain. So ignore it, I didn't say it. ;^)>
However, I really suggest Avast now to my Windows using clients. You can also, for now, stay with AVG 7. I am going to try Avira on a couple of my clients to see if it might be better. Most of my clients are businesses so they use the upgraded paid versions.