G5 Will Not Bootup... Options

[Injured Rezz]

Hi ive got a Dual 2Ghz G5 with 1Gb RAM, ive had it since december and has been running Logic 7 sweet. However i go to turn it on the other day and it will not boot up. I hear the chime noise and the fans start to run. But no display comes up at all. I have tried the apple help site and have tried restetting the PMU but it hasnt helped. The mouse lights up as normal, so i presume the keyboard is getting power as the mouse is USB'ed off it. So just to test its not the monitor for sure, i waited a while incase it was booting up with out displaying. I then pressed the eject on the keyboard to try and open the DVD, but nothing happened. The only other thing is if i leave it running for a few minutes the fans get faster and faster and sound like its not going to stop, so i power it down by holding the power button.

Any help would be grateful!