Computer Randomly reboots during games.

Okay, so I posted a thread previous someone tried to give me advice, didn't help seeing as how I checked out everything that he said to.

The only time the computer crashes is during gaming (World of Warcraft, Counter Strike, etc.)

Computer Specs
-XFX 6500GT Fatality (Nvidia)
-500W PSU
-2 Gigs of DDR2 Ram
-K9AGM3-FD/FIH MSI Motherboard
-5 Fans (1 Graphics Card, 2 Case Fans [1 Front, 1 Back], Processor fan, PSU Fan)
-2 16x CD Drives
-Hard Drive (Sata) 250 GB, 3 Gb/s, 16 MB Cache, 7200 RPM
-Processor AMD 690 X2

I have absolutely NO idea what BIOS is for, I've seen the Live Update 3 under the motherboard I have and was curious if I should do this update, not all my hardware is MSI, would this destroy my computer in anyway?

If it doesn't would it be possible to fix the problem? Would this make all the aspects in the computer cooperate and actually work? The specs on the computer are beyond what I should need to play a game such as that.

 

Also I need to know if reinstalling the operating system would help.