Crash on 3rd mission within a few seconds

I played starcraft 2's tutorial and first mission with absolutely no problem. Then I got to the 2nd mission and it crashed once or twice but wasn't a big problem or anything. Then finally on the 3rd mission (Hour Zero), within maximum 30 seconds the game crashes with this weird purple/green screen and I need to hard reboot. If you wait for a bit then the screen loses signal from the computer, and sometimes when you reboot the boot screen still has the weird purple lines and I have to switch my computer from the mains to remove it. (Picture below)
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I have tried downloading the newest drivers and the variables.txt edit, even reinstalling windows completely with hard drive format, nothing helped.

My computer specs are the following:
Video Card: NVIDIA GeForce 8800 GTX
Sound Card: M-Audio Delta AP 192
Hard Drive: MAXTOR S TM3320613AS SCSI Disk Device
Motherboard: ASUS Striker Extreme
Processor: Intel Core 2 Quad Q9300 @ 2.5GHz
RAM: 2GB Kingston DDR2 KVR800

Any help would be very greatly appreciated