I have been having this problem as long as i can remember, but i finally got the time to ask around. When i put almost any video in full screen, the video works fine for a couple of minutes, but then the picture starts getting laggy and so does the sound. But when i takes it off of full screen it works fine. I have checked all updates for my video card, and almost every piece related. I have a GeForce 9800M GTS 1GB. And i don't think its a virus because i do have a scanner/firewall. PLEASE HELP!