I just posted this in the Windows Vista NG, but then realized that I
might have a better chance here.
Family members HP Compaq/Older Athlon X2 just went belly-up.
Only sign of life is a single green led glowing on the mobo: no power
supply fan, no CPU fan, no response to DVD drive's eject button...
First thought was power supply, but when I swapped in a known good power
supply, no change.
Then I figured "Maybe the on/off switch"... so I pulled out the switch
and used a knife to jumper the two leads coming into it - figuring that
would duplicate the action of the switch... but no luck there either.
Unless somebody has a better idea, next thing I am going to do is to
revisit the power supply and verify correct voltage on each output lead.