I've got a strange problem with a lot of detail so I'll try to be as clear as possible about what I tried so far.
User was burning backups and left the pc unattended. A power failure occurred and although it was on a ups nobody bothered to shut it down so it eventually ran the battery down and died. The following day it failed to boot. The fan would give a half-hearted attempt to spin and then nothing. A few minutes of rest and then the same thing.
What I tried:
-put power supply in test pc and powered up fine
-put known good power supply in pc and pc started to power up but new ps started to smoke so I killed that immediately and replaced original
-disconnected everything except mobo and hd with no change
-disconnected hd and reconnected cd drive and powered up ok
-put known good hd in pc and powered up fine
-put hd in test pc as master and failed to power up (problem isolated right!?!)
-test pc will boot with hd as slave but not as master
-original pc will not boot with original hd as either master or slave
-replaced hd (200gig Maxtor on ide contoller pci card) with 200gig WD on ide 0, imaged old hd onto new hd and booted fine.
The problem now is that during testing the original problem occurred, but after few minutes of rest booted up and then no problems. Returned pc to user and first attempt to power up same thing. Then no problems. Today user says it won't power up at all.
To top that off, the ps that started smoking has been installed in a test pc and is still going strong.
Any suggestions on where to go next would be greatly appreciated!