Computer randomly shuts off

[nrshaffer21]

I've had my computer for a little over three years. I had it built at a computer shop in my town because I wanted a gaming computer. Ever since I got it it would shut down at random times while playing games. Due to pure laziness I never went back and had them fix the problem. Now the computer turns off after about 10 minutes of activity, game or no. Can anyone tell me what the problem might be?
Details:
Intel Core 2 Quad Q8300 Processor
Asus PN-D Motherboard
SuperTalent 2GB DDR-2 Memory
Western Digital 500GB SATA(7200 rpm)
Thermaltake WingRS 201 Mid Tower
Thermaltake TR2-430W Power Supply
Thermaltake TR2 600W ATX Power Supply
Asus ENGTS250 DK 1 GB PCI Express Video
Windows 7
Thank You for any help!

 

[Nyazzle]

You might be overheating, what cpu cooler are you using?

 

[nrshaffer21]

The stock cooler

 

[Nyazzle]

Then I'm 90% sure it's the cooler that's the issue, you can get a good cheap cooler at around £15, be sure to get thermal paste also and to clean the old paste off your processor with a microfiber cloth!