Q: Installation of OS Tiger on a G4 Power Book

Phone Apple and order replacements, or check sources such as Amazon or eBay.

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If the installation disc (grey in color) came with a particular Mac model that is not your Mac model, it usually does not work.

Also, if you are using a retail disc, there are other considerations.  By "retail," I mean a disc that was sold separately (in a shrink-wrapped box) for all supported Mac models.  Find your PowerBook G4 model on this list

http://www.everymac.com/systems/apple/powerbook_g4/index-powerbook-g4.html

On the profile page, find the Pre-Installed MacOS.  The version of Mac OS X on the installation disc needs to be later (up to hardware limits), not earlier.