My computer wont turn on someone please help!!!!

[Ams]

I was on my computer and and i left to the washroom and came back and it was off. I thought that a power faiure may have occured. I then turned it back on and after the windows login occured it shut off. I then turned it back on and after 3 seconds it turned off. I don't know what happened. I think my power supply may have broke but im not sure. Also sometimes when my computer is on and i leave it and come back to it it is like i left it in hibernate. Its on but i cant do anything or see my computer active. I dont know if that is relevant to my problerm but i would very much like some help. Please.
Thanks

 

[_-..zKiLLA..-_]

um i wanna say overheating but doesn't sound like it. so right now when u press the power button it does nothing? or does it still stay on for 3 seconds?

 

[Ams]

It now just flickers on and the goes off. I dont think its overheating because i left it cool down for over an half hour.

 

[A True Folder]

What are the pc's specs?

 

[Ams]

Amd Athlon 64 X2 3600, NVIDIA 7300 GT, Seagate 320 gb HDD, Asus m2n-e mobo, 1 gb ddr2 ram, and a 500 watt power supply. I dont think its the greatest because it came with my case for $50.

 

[A True Folder]

Can you try a different psu? maybe disconnect yours from the board and jump start it to test the 12v output?

Does the board look OK? as in no leaking caps etc

 

[Neodude1123201]

So the screen flickers,does the PC Make ANY Noises at all when the Power button is pressed?

 

[Ams]

Im not to sure as to how i would take out the PSU. The mobo looks fine there apears to have nothing wrong with it.The screen doesnt flicker and the pc makes the sound when you manually turn it off by holding the power button where it gradually gets quieter. If you know what kind of sound im talking about.
Thanks so far for the help.

 

[Neodude1123201]

Yeah,I think its definately the PSU.

http://lifehacker.com/software/repair/alpha-geek-how-to-replace-a-dead-power-supply-228626.php

 

[GhostGT]

I second that. I think its probably your CPU, especially with the described symptoms. That's how mine died, too.