I was getting this a few months ago, over time it became more frequent until one day I got a cmos error when I switched it on. Tried to reboot and pc didn't know any hard discs or cd drives where connected. After swapping everything, (mem, hard disc, cables, power supply, motherboard) it turned out that it was the processor

However I looked into the

driver_irql_not_less_or_equal

fault and this can relate to just about everything, just try to systematically rule out everything, if you have 2 sticks of mem, remove one, then try the other. Try graphics card in a different slot, try a different graphics card if you have one. Try machine with one hard disc at a time. Remove any hardware which is not neccessary, tv cards, sound cards etc

Also check the voltages coming from your power supply under load, a bad/faulty power supply can cause all sorts of problems

Good look