Power problems.

My CPU turned itself off. i wouldnt turn back on. when i tried it, it would make the usual start up noises. however, in half a second it would go off again. I waited for some time, and when i tried it again, the same thing happened, however the CPU took longer before turning itself off. during this process, the monitor didn't show any action, just went back to sleep mode. when i shaked the mouse, the monitor would pop on a second or 2 and then go back to sleep mode. when i reconnect the power cable or turn the button on the back of the computer off and on again, the computer would function normally again. however, after an hour or so the computer turns itself off again.
i suspect there's a problem with the fans, however since it doesn't matter how long i wait to reboot it, the computer will only function normally (showing any action on monitor) when the power is reconnected.
please help.

 

This sounds like a problem with the CPU cooler. Can you take the side panel off the computer and see if the fan in the middle of the motherboard is spinning when the computer is turned on? The fan should look like the picture in this link:
http://www.pctechguide.com/images/tutorials/MBoard/Heatsink4.jpg

Whilst you are inside the case, how dirty is it inside?

Another test would be to leave the side panel off and direct a desktop fan into the computer to see if it stays on for longer.

 

well the cleaning did it i think... well i'm still in testing fase but it seems to have helped... the fan WAS really dirty xD