Airport cards (made by apple) will only work in the airport slot of an airport capable Mac. It will not work in a PC Card slot.
Airport card is very similar to the Lucent Wavelan, with a few alterations to keep it from being used in a PC card slot
The reason being was apple's airport was cheaper than the wavelan which Lucent was selling at the time and in order to use the technology, apple couldn't compete with Lucent. So it switched some pins on the Airport keeping people from buying it for $100 then proceeding to use it on a PC at cheaper than Lucent was selling it for (almost double what apple wanted for their wifi card)
By making it only work in a mac computer with the special slot, it was the only way for them to get the technology, without directly competing with Lucent.
After that, when wireless came standard, the Airport Extreme was nothing more than a regular Mini-PCI card (I know, because I have used it in a PC) so it was electrically compatible with any Mini PCI slot. So there is nothing special/limiting about the Extreme that would keep it from working in a PC (Except a thinkpad, why oh why does Lenovo restrict people from using regular wireless cards in their machines???)
Either way, I threw an AP Extreme N into a Dell and it pulled up wonderfully. It still works to this day (at 802.11b/g/n in my friend's laptop.