I'm trying to upgrade a G4 450mhz (AGP Graphics) from OS 9.2.2 to OS X (10.4) and having no luck at all. The machine meets the minimum requirements for OS X (it has 768mb RAM). It runs fine in OS 9. I've got OS X 10.4 install DVDs from a new G5 Tower and new Mac Mini I've just got, and I've tried using both with the same result: The G4 will boot from the OS X Install disc, ask me what language to use, briefly say that it's preparing installation, then an alert message pops up that says simply: "This software cannot be installed on this computer." I then get to choose Restart or Startup Disk. I've checked the firmware on this machine, and it is up to date at 4.2.8f1. I tried downloading the firmware updater from Apple and when I ran it it said no update was needed. I had a spare ATA internal hard drive that already had OS X 10.3.9 installed on it (from a different G4, a 733mhz Quicksilver), so I stuck that HD into the G4 450, on top of the existing internal HD. When I try to boot from that HD with OS X 10.3.9, I get a grey screen with the "prohibitory" sign (think Ghostbusters logo without the ghost). And having this second HD in the machine doesn't change the "cannot be installed on this computer" response from the OS X Install DVD. I tried using the Disk Utility on the OS X Install DVD to reformat the original internal HD (after backing up), but it still didn't want to install after that. I WAS able to boot from an external firewire HD that has OS X 10.4.2 installed on it. So what's going on here? I might suspect that the OS X Install discs from the G5 and Mac Mini are set up to only work on those models of computer and thus won't install onto a G4, but that doesn't account for not being able to boot off a perfectly good HD with 10.3.9 already on it! Any advice or insight would be much appreciated. Thanks.