Thanks for your suggestions all,
i think the blue screens are software issues because they tend to ramble on about drivers
and stuff and are clearly linked to certain program installations that upset the system. But i also get slow game play after a while when playing DOW2 even though my GPU doesnt seem to get above 55C. It hasnt met my expectations but i'm thinking i just skimped on the GPU and need to upgrade, probably to a HD5870 when i can afford it.
The PSU isnt a branded one - i got it with a pentium 800Mhz system i bought about ten years ago. Like i say though- while it looks like its nicked from a WW2 bomber it performs surprisingly better than the newer 700w (not 500) EZCool which i bought a year or so and binned with almost no use because it was rubbish. I went on a site which added up the power requirements of all the components in your PC and i came out at about 380w so not sure how people are arriving at the 6/650 watt figure. Also not sure from the posts whether it will affect my overclocking ability but thinking of aiming for a corsair 650w in the hope this will improve gaming performance with DOW2. If not, i will be looking at a GPU uprade is suppose.