My PowerBook G4 1.5Ghz (loves it!) is missing 3 screws (two are the ones on the right side of the main housing, one is on the back of the main housing by the monitor hinges.
What kind of screws are these? I hope they're not something proprietary....
PowerBook Tech can sell you a set of screws for your machine. That website is generally a good source for parts for our 'books.