The Mac OS 9.1 CD included with the Apple Pro Keyboard only installs on Macintosh computers that came from Apple with built-in USB ports.
Symptom
If you attempt to install the Mac OS 9.1 CD included with the Apple Pro Keyboard, an alert box appears with a message that the installer cannot be used on your computer.
This would happen, for example, on a Power Macintosh G3/233 computer with an added third-party USB PCI card.
Solution
The Pro Keyboard Mac OS 9.1 CD only works with Macintosh computers that came from Apple with built-in USB ports. If you have a computer that did not come from Apple with built-in USB ports that is using Mac OS 8.6 or earlier, you must purchase the retail version of Mac OS 9.1 to be able to upgrade. If you already have Mac OS 9.0.x installed, you may download the Mac OS 9.1 Update from Apple Software Updates at http://www.apple.com/ .