My computer did this recently. Are you sure it cannot be the memory or motherboard slot? MY problem in the end was a dodgy slot, and we thought memory at first but it turned out it was the slot. So now I have 3 sticks of useless 512mb memory. I also kept getting video card beep errors from the bios, but it was not that. You could try one stick of ram on its own in the slot, and if it does the same then put it in the other slot, and then see if you have a change. I did this to diagnose my computer.