Computer keep crashing when **starting** 3D applications / games

Hello,
I've noticed this serious problem days ago when I was playing Star Trek Online. When playing, I switched out of the game to check IRC msgs. When I switched back, I only saw the game interface less than a second then my system crashes (no sound, monitor reports "No Signal" and numlock key failed too). I have to reset my computer. And within a day I can't even see STO's interface; the computer crash instantly after loading screens. Then when I try to use 3D window switch of Windows 7, same thing happens sometimes. I then tried other 3D games like TrackMania, and I could only see the rotating globe (3D) for a fraction of second then my computer crashed again. It seems that any 3D rendering would crash my system.

The strange thing is I could run some other applications which use GPU at 100% but with no 3D renders, like miners of cryptocurrency.

I'm not overclocking my system.
Checked CPU and GPU's temperature and both are fine.
Tried minimal system, no luck.
Tried many drivers from 275.33 to 290.xx beta, no luck. I was using 285 driver without any problems.

System spec:
CPU: AMD Phenom II X4 940
Memory: Kingston 3 x 1GB
MB: Gigabyte MA78GM-US2H
GPU: Galaxy GeForce GTS250

Any help is appreciated, it's driving me crazy these days.