Mac OS X Install disk

What are the 2z-***-***-A numbers on it & the color & wording please?

You can boot using the DVD and ......
1. Run First Aid on your hard drive(s) to fix errors
2. Erase/reformat your hard drive
3. Reinstall the base OS 10.4.x & applications

 Cheers, Tom 😉

2Z691-5599-A is a pre-release Developer's version, so I can only guess that it should work with all G3s & G4s, & possibly earliest G5s.

Tiger was released to the public on 29 April 2005, so it may not work on any Mac around that or later.

Does it boot from it fine? Holding c key down at bootup?

"Try Disk Utility

1. Insert the Mac OS X Install disc, then restart the computer while holding the C key.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)
*Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.*
3. Click the First Aid tab.
4. Select your Mac OS X volume.
5. Click Repair. Disk Utility checks and repairs the disk."

http://docs.info.apple.com/article.html?artnum=106214

You can see other options in that menubar too.

Do you perhaps have firmware password protection in Mac OS X ...

http://support.apple.com/kb/HT1352

It would block usage of all the startup keys, like C, N, T, D, CMD+s, CMD Option+pr, CMD +v, Option, and Shift.

Try holding the Option/alt key down when booting up... do you eventually get that as a Startup choice?