Normally, the installer will tell you that the disc is intended for a different machine. The MacBook disc panicked it because MacBooks use Intel processors, which are completely different from the PowerPC in your PowerBook. Interestingly, while most restore discs are tied to their original hardware, some aren't. The only one I remember of the top of my head is that the eMac restore disc will work on any PowerPC Mac, but I think there are a couple of others.