Been encountering random Auto Shut Down / BSOD when doing normal activity since few weeks ago.

This is what I usually encounter before running into Auto Shut Down / BSOD.

1) When browsing youtube / facebook, pc random shut down / BSOD.
2) Watching HD movie with Media Player Classic halfway, PC Shut Down.
3) Playing game halfway, Dota 1 & 2 randomly shutdown

PC Specs:
Intel Core 2 Quad Q8200
4GB RAM
Nvidia Geforce GT 630
WD 500GB HDD
Window 7 64-bit


Please help! attached ScreenShot.


Attached thumbnail(s)