My daughters mac mini (pre intel) won't install leopard (10.5) even though it seems to meet all system requirements. The only thing I could think of was that the system wasn't formatted correctly to upgrade from tiger to leopard. I erased the system but I used disc utility on the OSX 10.5 installer, and in retrospect that was dumb - I should have used the 10.4 installer. Now the computer won't accept 10.4 or earlier installation discs, apparently because the driver for those systems has been erased. I can boot with the 10.5 installation disc but it won't install. Is there a way around this mess I got myself into? I have an external hard drive I use for backups. Can I put the 10.4 installation software on that hard drive and use the external hard drive as the start-up disc? Will that do anything bad to the external drive which is partitioned for Mac and PC backup?