Okay I just upgraded my computer. It was before:

Manufacturer: Compaq
CPU: AMD-K6 500MHz
Motherboard: -Don't Know- (Maybe SIS?)
Memory: 312MB SDRAM PC133
Video Card: Voodoo3 2000 PCI
Sound Card: -None- (Integrated: ESS)

Now Its:

Manufacturer: Compaq
CPU: AMD Athlon Thunder Bird 1000Mhz 266MHz FSB
Motherboard: MSI-6380 KT7266 Pro2 266MHz FSB
Memory: 256MB DDR
Video Card: GeForce3 Ti 500 64MB DDR
Sound Card: -None- (Integrated: Avance)
And a new case, ATX 300W

When I first booted up my computer, I didn't change much in BIOS. But later on when I was trying to fix this Problem, I changed some things but then I just set it to BIOS Defaults anyway.

But the problem is that when ever I exit a Game (Expecialy Operation Flashpoint) the computer Restarts. And most of the time I lose all my information and my configurations reset! I cannot figure out what is wrong! I tried this one thing that someone mentioned, disabling Wake-Up options in BIOS. That didn't work.