[Troubleshooting] Computer Crashes When Loading Games

I built my PC a couple of years ago and it's never had any major problems until recently whenever i get to a loading screen in a game (I've tried it with Left 4 Dead 2 and Borderlands, and it only seems to be bigger games. Terraria and my indie games work just fine.), the screen goes black and the motherboard beeps, forcing me to reboot. I opened it up and took out all of the dust (it was VERY dusty), hoping that would fix the problem, but that didn't work. Here are my specs:

OS: Windows XP Video Card: NVIDIA GeForce GTX 260 Processor: Intel Core 2 Duo CPU (3 GHz) RAM: 3.3 GB Motherboard: Gigabyte EP45-UD3R Power Supply: Antec 700W