G5 Dead? Zpping PRAM, resetting NVRAM and PMU don't work...

First of all sorry, I'm new to this forum and unfamiliar with your etiquette so sorry again if this has been taken care of before.

I own a Power Mac G5 (the first model on this page: http://support.apple.com/kb/SP96 ). It's been running pretty smoothly up with the occasional hang ups, but nothing I wasn't able to take care of myself). Today, after two or three attempts to work on it, the whole system froze and I was forced to shut it down manually. Since then, I haven't been able to get into the OS. Here's what happens:

-The opening chime and fan work as usual, the first couple of times, the computer would sound as if loading, but it would not show anything but a black screen and I am forced to shut down manually, again.
-After resetting PRAM, every time I open it up, it reaches the grey screen with the Apple logo, but after a few seconds of the spinning gear, everything freezes and again, force shut down.
-Looked around all the forums, tried zapping again, tried resetting NVRAM, resetting PMU, did a fsck -fy check up tried to start in Safe mode (nada), tried to boot from disc, can't even reach it. Tried using the option key while loading to get the choices, still nothing.
-I've tried leaving it alone for extended periods of time, nothing...

I'm out of ideas and have a very bad feeling about what this all means... What could the problem be? I haven't installed anything new on the computer which I mostly use for ripping my LPs and to record some of my own music using Ableton Live.

Any hints, clues or help would be greatly appreciated.

PS: I forgot to mention that even though the screen freezes, the computer seems to still sound as if it's working or booting, but nothing else happens and every time I'm forced to quit manually.

Message was edited by: Boro76