Reading through your topic thread, the PowerBook G4 with FW800 would be circa 2003.
You can download MacTracker from their site: http://mactracker.ca for detailed info on
most every Apple product with specs and system info. To use this, you'd need to know
the build model, based on Apple sources.
The PowerBook G4 5.1 and 5.2 are somewhat similar; if you were to search by serial
number or find other correct identifiers on the computer, so as to match the OS X version
and original grey label DVD install-restore set (through resellers online) the correct disc
set part numbers could be located. Pesky details...
The computer would otherwise be able to use Leopard 10.5.8 from a lesser retail version
of 10.5, and there still is a download update to 10.5.8. Other parts not on a retail DVD
would be found on other discs you could buy. The iLife, AppleWorks or earlier iWorks,
and others may still be found through online vendors, auctions, or maybe if you contact
Apple User Groups in your area, or check out moving sales, college/school rummage sale
or university clearance of old hardware, some of these may still include old retail full install
versions of OS X and Apple software that won't work on the newer Intel-based Mac.
You may have to look into online resellers to see if any have the retail label Leopard 10.5
DVD install disc. Amazon resellers may have these on occasion, but they are rare now.
There used to be a time a few years ago, when you could have contacted Apple support
and paid a reasonable fee for a white-label "replacement Leopard 10.5 DVD" that covered
the older hardware versions, they offered (also, quietly) a similar "replacement Tiger 10.4"
white label full install DVD. Both of these were a hit & miss affair to see if they had any,
if you happened to contact someone at Apple sales support or applecare who knew they
may exist and knew to also look. They were under $20 each, direct from Apple and not
available in the online store. Some independent Authorized Apple service providers used
to have a complete set of system and technical discs; some of them could burn you a copy.
But not anymore. Most people don't want to touch the older models, on the retail side.
Hopefully you can find a clean retail copy of the Leopard 10.5 DVD, there also was a source
online to download an Apple Hardware Test for certain models that used to come with one
on their original install-restore disc media, when new.
If nothing else, there are some now-discontinued MacBooks (circa 2006 to 2010) out there.
Faster, intel, and they can run Snow Leopard 10.6+ & still some older PPC applications.
Good luck & happy computing!