My custom built desktop has been having a problem for quite sometime with randomly shutting down (usually when doing something intensive, such as starting a video game or loading a level in it). The machine will just die (as if someone pulled out the power cord) and then will have some trouble turning back on (the button doesn't respond for a few seconds).

Some things I've tried so far is to replace the motherboard and the graphics card, and to check the temperature settings (it's not overheating, temperatures are actually quite low).

I guess I've pretty much narrowed it down to either the power supply or RAM, but I'm just seeing if anyone has any insight on the problem or if it's happened before.

Let me know if you need any other information, thanks!

It might be PSU related, but not in the way you think, it sounds like your computer and power supply are overheating during game play and shutting down.

Check and make sure all of your fans are working and that you have a heatsink rated for your processor.