it cant be overheating, i used Rivatuner to put my GPU fan to 100% and the stability test temperature stoped going up at 56c, then i tried playing L4D with the fans at 100%, the temperature was only at 48c but it STILL crashed.

Im also not sure if its power either, i used a PSU wattage calculator, and it said that the PC should only require 438Watts. though maybe its a faulty PSU, Im not sure. it was certainly A LOT cheaper than the PSUs by the companies you sugested.
there is one more think i can think that could cause a problem, my room has only one accessable socket, so i have had to overload it with splitters. My PC does not work when connected to any of the splitters because it needs all the power the socket can supply. so i solved the problem by running an extension cable under my door to an available socket. the thing is, this extesion cable ends in a 2 way splitter, i asumed that since i dont use the other socket on the splitter it shouldnt split the power from the socket and my PC should get it all. maybe the Splitter still reduces the wattage that should be getting to the PC, causing power problems. but that sounds unlikely.

a PC enthusiast i know suggested it could also be faulty drivers or an OS problem, is this posible?