Right, i have a Powerbook G4, that was running OS X 10.3. I wanted to upgrade to 10.5. I've checked the specs and the powerbook is capable of running Leopard. The Powerbook said that 10.5 couldnt be installed. So i decided to install 10.4 and use a 10.5 upgrade disc i got with my Aluminium Mac. 10.4 required the disc to be reformatted with a GUID Partition Table. So i did that and tried to install 10.4. But it wouldnt read the disc. So i connected it as a Target Firewire drive to my Mac, and installed it from there. The Install succeeded. But now when i boot the Powerbook all i get is a folder with a flashing question mark in it. And it wont go any further. BUT, i cn boot my iMac from in 10.4 using the Powerbook as the startup disc. Could there be a problem with what would be the equivalent of a BIOS? Thanks for any help you can give. P.S. Ive tried booting from a cd, clearing the PVRAM, both to no avail.