Get start-up chime, gray screen, then shuts off

Question

I have an eMac that will start up, but once the screen turns gray and the gear starts going around in a circle, it powers off. I tried to read some of the other posts.
1. I tried unplugging the cord from the computer for a while - no change.
2. I went into the open firmware and did those three commands - it stayed on long enough to do that and then when it restarted - no change
3. I did a cmd-option p+r, I forget what that is called, but... - no change
4. I hooked up my firewire drive and was able to boot from it. I was going to do a netrestore, but the HD was not in the list for target source. What does that mean?
I am a computer teacher new to Macs and any help is greatly appreciated.
eMac   Mac OS X (10.3.9)  

Answer 1

Strange; not that Disk Warrior was able to repair your hard drive --- it has an excellent reputation for that --- but that a damaged disk directory (which is what Disk Warrior repairs) would cause the Mac to shut down. The expected failure mode for a severely damaged disk directory would be to see it stuck at the grey startup screen (lesser directory damage can manifest as unvalidly large untrashable files; e.g., a 128 GB file on a 40 GB hard drive).
In your place I'd be working feverishly to make sure all my data is backed up (and verify the backups). Something's not right. If you open Disk Utility, what's shown for the SMART status of the drive?
Opening up the eMac to replace the hard drive is a non-trivial process and requires care, both to avoid the dangerous voltage levels on the CRT yoke and to avoid damaging the power button leads, and of course voids any remaining warrenty, but plenty of people have done so (try Googling "Apple eMac Upgrade Guide"). You can find internal hard drives from 40 GB to over 300 GB at prices from US$80 to $600 but figure somewhere in the $100 - $150 range for the drive.