I have a new system which I felt needed a better power supply so I swapped out my generic 500w without the sound issue for a Hiper 720w power supply, the only problem with this is that whenever I play games which use alot of graphics and cpu I get a noise that sounds like the hard drive but is being omitted from the psu. I then replaced that 720w with and 650w which did the same, if I have the game minmised the sound disappears as soon as it maxmised the sound returns.
Any help will be appreaticated unless you tell me to get another psu and no I don't have the 500w psu anymore.
You've determined that the PSU is the issue, but you don't want to get another one. Then you'll have to determine what component causes the noise and replace it by a better one or totally redesign the circuit to get rid of the noise when the PSU load is high.