When I say friend what I really mean is guy I know from school who added me on MSN to talk about PC's because I'm "that guy" who knows about building PC's and such, so I'm not inclined to help him that much when he had the stupid knowledge of "Get a cheap PC, buy expensive GPU = Awesome gaming PC". When will they learn?
^^ I've run into more than one of those types when I was at school, they don't really want to learn. Best way out of this is just tell him his computer "doesn't support graphics cards" and leave it at that. Don't get too involved in case he actually tries to fit a GTX 580 and blows up his PSU, he might start blaming you.
He'd never be able to afford a £400 GPU, let alone even know which is the best. So far I've just avoided speaking to him now anyway.
The thing is, you won't get anywhere, because the psu most likely will be able to supply its rated power, however it will be a "burst" rating (not continuous). It's exactly the same situation with amplifiers that I work with. I have a couple of Powersoft amps that are rated at 20kw, the thing is they can only supply that amount of power for a short period of time before the supply rails need to recharge themselves. You're more likely to get about 12kw continuous power from them. The only way to check is to attach a dummy load and a multimeter to see what's actually going on. And remember, power changes with impedance. The lower the impedance, the more power the psu will be able to supply.
