G5 boot problems, please help :-)

Hello everyone,

I have a PPC G5 (I think it's an early 2005), it's a duel core with 4x 512mb ram (2gb) and two hard drives (one 250gb and one 1TB) and running OSX 10.5.8

AND I am having some real problems with it and really need some help. This is a long story so I'll start from the top:

Everything was running perfectly until one day the G5 froze up during normal use, the little colourful spinning mouse cursor was spinning away so I left it to work it's self out, however the fans started spinning up faster and faster and louder and louder, so for the first time ever I turned the G5 off by holding down the power button. Next time I started the G5 nothing happened, no start up "bong", the power light was on but nothing started and then the fans went crazy again. The next time I turned the G5 on everything was as normal, booted up just fine, and about 15 minutes later it froze up exactly the same again. The next five or six boots were just the same as the "light on, no monitor display, fans go crazy".

I then managed to boot the G5 in safe mode but again after 15 mins it froze and fans go on full. Then another five or six unsuccessful boots and would not let me boot in safe mode. Luckily I have a friend with a very similar G5 so I started swapping parts to test out, first was the Ram, they were all ok, then I changed the little battery, all ok again. So I tried a few more things, I reset the nv-ram, no difference, I then booted in single user mode and did some more resets, still nothing. I then tried to boot from CD, this looked like it was going to work, it made lots of (good) noise, it was clearly reading the CD, I got as far as the grey apple loading screen then after 5 mins it froze up/fans went crazy.

The next ten boots were the usual unsuccessful no bong no monitor crazy fans, it was almost as if it wasn't reading (or paying attention to) my keyboard commands, command-c etc.

So lastly I tried reseting the Pram (button on the motherboard) and now it's the same as before but now the power light does not come on.

This is where I am now, it's also worth noting that the machine is immaculately clean inside, not a single bit of speck of dust.

Anyway, any help at all would be massively appreciated. If you can help thank you so much, otherwise thanks for at least having a read :-)

Thanks again :-)

Addi