According to Macfixit, Panther (Mac OS X 10.3) won't be compatible with pre-USB built-in Macs! Apple is going to be considering all machines older than 5 years obsolete. Or so Macfixit was told by an anonymous source from Apple. Here's the report before it disappears into Macfixit's pay only portion of the website: If you think this is wrong I suggest submitting feedback to <http://www.apple.com/macosx/feedback> A sidenote: Powerbook G3/333 and 400 without Firewire but with SCSI (a.k.a. Lombard model) have been known to have issues installing Mac OS X in the past or running it due to a problem on the motherboard, which if fixed can make those machines work with Mac OS X.