I would advise you to post in a tech forum like tomshardware.com or guru3d.com. Power supply failures are extremely rare, I have been fixing, building, repairing computers for a long time and I have only seen the issue being a faulty PSU once.

Try googling "stress test" programs like Prime95 for example, let it run until failure and see if you can diagnose the cause. Any overclocked parts should be set to their default values. If all else fails re-format before buying a new part. You could buy a new PSU and find out it was not the issue. It could be a corrupt Windows System sector on the HDD, or video driver failure, so many other things.