Guys,
After changing the power supply as I mentioned earlier two months ago solved my problem but today strangely enough while playing another game named as Apache Longbow Assault, the same thing happened, all of sudden shutdown and restarted automatically. I layed another game named Apache Air Assault made by same company but I could play it for half an hour, but this almost similar game shut down and restarted my computer.
Does that mean, that I need a power supply more powerful than my current 400 watts PSU????