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I can't turn on my box anymore, and I can't diagnose where the failure occurs.

  1. The LED on the motherboard itself is on when the power supply is on.
  2. When the power switch is pressed, the fans start for a split second but then they stop.
  3. Can't seem to turn it on using the power switch pins directly.

It's almost the same with another (healthy) equivalent power supply, except the fans do not even move.

Does it mean my motherboard is toast, or should I be looking elsewhere?

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I'm fairly certain this is covered in "Dean's Electronics". Maybe you lost your copy? :-) – Joe Internet Aug 13 '10 at 8:04

If youtried with a good power supply and you eliminated a switch failure, all it remains is your motherboard. However, this may be a minor problem, so before throwing it out go to a computer service, maybe they can fix it.

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sometimes reseating the cpu and ram can help, but i've had this twice in the past that as just a toasted motherboard.

It can also be duff PSU, but it sounds liek you've tested that to some degree.

To be honest, One time this happened it turned out to be a loose screw on the back of the board shorting it up, and one time it was a spare metal riser post for other form factor motherboards, so it could be a lot of things but start with the easiest to check.

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up vote 0 down vote accepted

Turns out it was... *drum roll*... a dead video card! Removing it brings the power back. Putting it back makes the symptoms come back again.

Oddly enough, I found it out accidentally while trying to reseat a CMOS battery (as some posts suggested elsewhere), which I did, but not before removing the video card that got in the way.

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