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I have a Leopard disc too that refuses to install on some Macs (like an eMa, G4 Power Mac) yet installs fine on a G5 Power Mac. I installed it on the other older Macs by using Disk Utility to create and image of the DVD, copying that image to a USB hard drive, and then installing Leopard from the USB hard drive instead.
 
Jackpot! Restored then it recognized my partition as a start disc; currently installing.

So was this was a software issue with Panther 10.3?
 
I was having the same problem so i connected a spare hard drive to my Mac formatted it and all that and restored the software from the cd to the hard drive restarted my Mac held down the option key and the hard drive was there so I booted from that and hey presto the hard drive started the leopard install I just did erase and install and it all works fine I hope this helps other people that are having this problem
 
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