AVG 8 has become a resource hog...like Nortons.
Avoid it. I have been using AVG 7.5 for quite awhile and it was ok but the ver 8.0 will slow your system. I had it on a few different systems from dual core Opteron's to core 2 duos and they all slow quite a bit.
I've now moved on to avast free home edition..works very smoothly and doesn't hog system resources. System speed up is quite a bit.
http://www.avast.com/eng/download-avast-home.html
Of course also use Spybot and a fire wall.