Fulmar, take my PC. I used onboard for about 3 weeks and could not stand the bad sound. During games when explosions came up, the sound would go blank. I am now considering getting a better soundcard to replace my Audigy Gamer from 2004.
He may have a trojan, but I doubt McAfee would find it. He's probably better off installing ESET NOD32 or Smart Security suite. I agree with Skuzzy in that especially those two AV's, should be considered viruses.
Where he'd benefit most from is an 8800GT or comparable ATi card, depending on his liking. Also, 4GB of matched RAM and a beefier PSU. But, this might move the bottleneck to his CPU.
I guess I should have been this clear. His problem doesn't seem to be in "one area".