Make sure the iBook is capable of running Mac OS X 10.5.
If so, Leopard is probably going to cost you more than the iBook is worth.
I was unable to find the serial number after login onto the Web site to Apple customer support .
The serial number to the iBook g4 i registered few months ago !
If Apple would remain competitive and allow customers to download Leopard , then Apple could earn market share which would prove useful in a supra-hyper-compettive information age not only computer age . Influence would count too .