Cannot install Leopard on G5 Powermac

Let me explain. I have a G5 Powermac DP 2.0GHz that I recently received from a friend. Currently I have Tiger on this system, I am trying to install Leopard on this mac though when I put the install disc into the mac, it sees the disc and it seems to be reading it but it just shows the grey screen with the apple logo and the spinning dash wheel. I waited around 20-25 minutes on that screen and it goes nowhere. Though during this time I noticed that the powermac's fans kicked up gradually to 100%. It became really loud though the air coming out of it was cool, not even warm. Anyways, I guessed that maybe the disc is having trouble reading. So I tried to make a image of this disc and restore it on a usb external drive. Again I noticed after the fact that PowerPCs cannot boot from USBs. Unfortunately, all I have is USB drives, unless I use my sole MyBook (Has a lot of free space) which can connect via Firewire but I need to know that an image to MyBook will not delete any data from the drive because I need all the files on that drive.


Anyone help a new mac user out?

 

Hey guys thanks for chiming in! Though I managed to install leopard which I am currently typing on via copying the image of the DVD over to my harddrive and then restoring it onto a spare sata drive that I had from a xbox 360. It was a notebook drive but it connected and sits perfectly inside the G5. Once I restored the image of Leopard onto the harddrive it worked great no trouble what so ever. Anyways, thanks again for the help.