Hi I have a new PC AMD Quad core phenom with a 450w PSU and a 1GB 9800 Nvida Card.. The PC was working fine but then every now and again the PSU made a funney loud whiring noise on startup that then went quiet... Twice noe in games the PC has just cutiut and died it will restart straight away but the case and PSU is redhot to touch... DOes this mean my PSU is screwed? Other Times like now its fine!
I would just take my psu out and open it up. Just look at the capacitors (the small cylinders) and look for leaks/burnt tips. If you've ever seen batteries that have popped, it may look a lot like that, with acid residue on the pcb. Even if you could get your PSU to work again, if it has damaged capacitors, it is a ticking time bomb.
Invest in a new solid PSU (something you can use for your next build). That's exactly what I did when my PSU blew up a few weeks ago.