PowerMac g5 won't install Leopard

Hi,

I I recently bought a PowerMac g5 early 2005 dual processor at a surplus store for $2. A STEAL I know.

All it needed was to flush and rebuild the watercooling components.

I bought a retail disk of OS X 10.5.1 to install on the machine, and a new hard drive.

After powering on the machine I hear the chime and see the folder and the question mark on the screen. This was my first indication that the computer actually works.

After loading the install disk and holding option, I can see the disk in the menu "Mac OS X Install DVD". I can click on the "go" arrow, and the grey screen with the Apple logo appears.

I do not see any loading icon below the apple logo however. The machine stays motionless on the apple logo for several minutes, then powers off.

Could you guys help me figure out what is holding up this install?

I have tried resetting the NVRAM with cmd, opt, p, and r.

I have replaced the battery in the motherboard.

I have reset the PMU using the on-motherboard button.

I have tried swapping out the RAM

Also, the fans all kick up to full speed a few seconds after the chime. All the fans are installed, and the plastic shroud is in place. There is no red light on the motherboard. I read that the machine may need thermal calibration since after i removed the CPU's. Is that the case?

Thanks a bunch guys.

PowerMac, Mac OS X (10.5.1), g5 dual processor