I work with my computer but no power signal in the...

Question

hi to all of you there!!! my problem with this asus A7S333 is that no power signal comes out but the power supply is functional..this problem occur when i played a game and when the supply of electricity in our street has shorten my computer restarted again and again..even the monitor has been affected by this problem..

hope you will help me with this kind of problem..
thanx