G5 tower won't boot; fans ramp up until I shut down

I'm running a Dual 1.8 GhZ PowerPC G5, with 1.5 gig of RAM. I recently replaced the power supply, as the one that came with the machine died.

I left the machine running last night, and this morning I found the fans ramped up as high as they could go, and the screen telling me that one of the external devices had been disconnected improperly. (This had happened once or twice while I was using the computer before I went to bed. Couldn't figure out what the problem was.) I shut down the machine by holding down the power button. When I turned it back on again, it wouldn't boot. I get the startup chime, and the main HD spins up, but the screen remains blank (the light on the display still works the way it should).

I was somehow able to get the machine to start from my backup drive once, so I verified and repaired the main drive. It checked out fine. I tried another restart, and the machine wouldn't boot again. It has since refused to boot, getting no farther than the startup chime.

I've tried pressing the power management button. I've tried booting from the Leopard disks, and I've tried zapping the PRAM. However, it appears that the keyboard isn't having any effect, as the last two didn't work either.

Anybody have any thoughts? I've removed and reseated one of the RAM cards, but haven't had a chance to try the rest yet.

I can't afford a new machine right now, so I'll try pretty much anything to get it to work again. Thanks!

UPDATE: I removed the Belkin PCI card I had installed in the machine, and it started up with no problems. So, it would appear the card is the problem. It's been working fine for months. Is it possible that it just up and died for no reason?

This is the card I had in the machine:

http://www.staples.com/office/supplies/p1_Input-Output-Cards_157547_Business_Supplies_10051_SEARCH

And NOW, one of the internal drives won't boot.

Firefly2002 said:

Well at least the other(s) work(s)

Got DiskWarrior?

Click to expand...

Yes, but it's not much use when it can't even see the drive.

I borrowed a case from somebody. I'm going to throw the drive in there to see what happens.

Put the drive in a new case, and it works with no problems. (Disk Utility found nothing to repair.) So, it seems something is wonky with the connections inside the machine.