Officially, almost nothing. Hard drives and RAM, as somebody else mentioned. Not logic boards, screens, or even the top case. You could probably get away with the clutch covers though. ;-) You might be able to swap optical drives, though the cable placement and drive size can vary, and there might not be the proper mounting hardware. However, if you really want to swap things, you can generally swap anything between the same revision; ie between the 400 and 500, or between the 550 and the first 667. Malcolm Cornelius <malcolm at fireflyuk.net> writes: > Can anyone help me as to which parts from a 400 can be used in later > machines and the reverse. > > Are the screens, CD/DVD etc. interchangeable ? Kynan Shook kshook at mac.com http://homepage.mac.com/kshook/index.html