eMachines windows xp trouble

I am no computer whiz but my desktop just went dead. The keyboard was blinking and the tower would not cut off until I unplugged it and then turned it back on, same thing. Now it odes nothing. Moniter works fine. My brother rplaced the power source and it does the same thing as I mentioned above. Power light stays on and fan runs, that is all?? I need help Please.
Thank you,
Marty
further post
processer is intel celeron 2.2 ghz
memory 256 mb
hard drive 40 gb
power supply bestec
video card onboard video emachines

You need to post your exact pc specs so we can further help you, thx.

Mobo,
processor,
memory, hard drive,
power supply
video card, rather its onboard or an added card

And also don't double post the same issue. Only post 1 time please.

eMachines owners of 14 models built since 2003 have been plagued with totally failed motherboards, that destroy the power supply as they fail. There are multiple posts on eMachines with some disagreements on failure. Some techs believe the failed power supply destroys the motherboard. We feel it is the motherboard failing that causes other problems. Search the forum, and if you concerns are not answered, get back to us with the eMachine model number and its age.