Just open the PowerBook up - take away the battery, remove the AirPort Extreme card from its place and see what's written on it. If it goes "Model No: A1026" then it won't work.
I haven't take it out yet, but the system says "Broadcom BCM43xx 1.0 (22.214.171.124)" so i think there's a big risk that it is the A1026
Change the AirPort card to a not so old one.. can that do the trick?
Henry Lerche Rasmussen