I built a new PC a while back, specs are: Intel QX9650 Asus Striker II Formula 780i Motherboard 2x 512Mb Geforce 8800GT in SLI (Asus EN8800GT) 4Gb Corsair 800mhz ram. Asus SupremeFX II Audio card (Came with the motherboard) 1000Watt power supply 250Gb hard drive for my OS, 500Gb for data storage. Vista Ultimate x86 My problem is that when I'm watching some video, every so often the video will get colourful lines through it and a square block will show around my cursor. Photograph of screen: link If I move the cursor around after it "glitches", within a few seconds the machine locks up and my monitor goes blank. All I can do is restart the machine. Anyone know what is wrong? I have the latest driver for the graphics cards. I have a friend who gets the same thing in vista, but says he hasn't had it happen at all in XP.