Computer randomly restarts, won't stay on for more than 2 hours

[shaun7787]

My computer randomly restarts whether I'm playing a game or downloading something or it's in sleep mode. It will stay on for a maximum of about 2 hours and a minimum of 5 minutes. The screen just goes blank and then it reboots. I checked the temperatures, they are all normal (CPU, MOBO and GPU all around 30 celsius). I've been having this problem for a while, and since then I've upgraded my mobo and RAM, so that possibility is ruled out too. I'm thinking it may be a problem with the power supply but I'm not sure. please help

Specs
MSI Z77A-GD65 mobo
Intel Core i7 2600
nVidia gtx 580
Corsair GS800 watt PSU
Intel 40gb boot SSD
western digital black caviar 1tb data HDD

 

[ddan49]

Did you scan for viruses? If not hardware, then software.

Also, even though you upgraded your mobo/RAM, you could still have a faulty part. Do a memtest on your RAM to make sure. It doesn't seem like you're using too much power, but the PSU is commonly a problem. Even Corsair can make a bad PSU once in a while!