PC Shuts itself Off

Specs are in sig. I thought it might be the PSU, but this 520W should be able to handle it no problem. I only get problems when I'm playing borderlands.

Are you overclocked? First thing id do is make sure your OC is still stable (if you have one).

2nd, if it only does it in Borderlands, check your graphics driver. Make sure you are running one of the latest drivers and be sure to uninstall the drivers completely (driver sweeper, delete files.. some say its not needed but Im old school and like to remove it all).

If that doesnt work out, Id try memtest86 and check for your ram (or pull a stick of ram and test each individually).

Its possible its your PSU, but with only random shutdowns during Borderlands, Id think about a possible SLIGHT instability in your OC or graphics driver error. Also, check windows event viewer, see if it logs anything right before this occurs. May give you an idea to the problem.

Ahh windows event viewer says it shuts down because the gpu is overheating. ATI fail

Set the fan speed in CCC. I have mine set to 32% on my 4870 without an issue on the stock cooler. Keeps it 70c or cooler.