iMac G5 won't boot from CD drive, Please Help

My iMac G5 won't boot from the CD drive. There is no operating system on the hard drive so I want to install a fresh copy of Leopard. I have tried a couple different methods, but I keep getting the same end result. The first method I tried was booting from the CD drive by holding the C key during start up. The Leopard disc was automatically ejected after about 20-30 seconds. The second method I tried was booting the iMac to the "question mark file screen," which is when I inserted the Leopard disc. Usually on other Mac computers, this is when the computer will show the Apple logo and prompt you with the installation process. Not this iMac, it just ejects the disc shortly after I insert it. I'm not sure if it's the CD drive that is having the issue, the hard drive, or something else.

If you have any ideas, they would be greatly appreciated!

Thank you,

Chris