I recently started having this problem in that whenever I play a graphics intensive game (dishonored, assassins creed, battlefield 3, even minecraft), my PC will power off after a few seconds. For the few seconds when the game is on screen, my PSU makes this odd noise that is like a tick/chirp/sparking noise (kind of hard to describe, if necessary I could probably record it) which becomes slightly more frequent over the seconds until the power off. Minimizing the game can stop the noise/power off, and bringing it back will start it again.
The strangest part to me is that all of my games worked fine until about a week ago when I switched from Windows 7 to 8. After the switch, this problem started. This made me think it was a bad driver at first but I've ruled that out now.
I also checked to see if it was overheating, but that isn't the case.
I am sure it is the PSU making the noise and not the GPU or CPU.
I tried switching power cords to no avail.
When the power off happens the event viewer shows a kernel-power error (41) with details of
i5 CPU 750 @ 2.67 GHz quadcore
4 GB of ram
Gigabyte H55M-UD2H motherboard
Radeon HD 5770
30 GB SSD (the OS is on this one)
1 TB HDD
PSU is xtremegear 950W
I have been reading about PSU's and I guess the consensus is that Xtremegear is not good quality and can fry systems so I'm a bit worried to keep trying to fiddle around with my machine. I've had all this system for ~2.5 years so it might just be old age, but I'm having a hard time believing that it's a coincidence it happens when switching OS's.
your psu voltage reading should be in those specs http://pcsupport.about.com/od/insidethepc/a/power-suppl... but with those noise if that psu is still under warranty i ask for rma, also close all the light and look in if you see any spark from the inside of the psu stop using it before it damage parts on your computer