Power Mac - start up problem

can anyone give me some good advice on a problem i am having with my dual 2.5 G5 mac?

a while back (after a software install) the fans began getting really loud (apparently not a big deal). I didnt use it for a few moths at all, left it turned off, went to turn it on one day and it never got past the grey screen with teh apple on it {the gear never showed up} shortly after power up the fans really kick into high gear but nothing else happens. i replaced the pram battery (guy at radio shack pronounced it dead) g5 still never got past the grey screen.

i tried resetting the pram {apple option p & r keys} it never would reset, never made the start-up sound again that is. I cannot start it up in safe mode, i cannot boot it from the install disc. i can hold option while start ing up and get teh screen that asks what directory to start from, but no matger what i choose it goes grey screen, nothing more.

i hooke dit up to my iBookg4 via firewire and can see and access the hardrive just fine, i cannot however get it to run the disk utility to maybe repair any bugs it may have.

is there a way i can re-instal the OS in teh G5 via firewire form my iBook?

or am i maybe looking at a hardware/board isssue?

any advice will be greatly appreciated so long as its not anythign i have already mentioned doing,

thanks

j_i*:black: