Did you get the wireless card or the actually Airport Extreme Base Station?
The wireless Airport Extreme card is for installing into your mac, which is usually only needed in the older macs because new macs come with wireless cards as standard. I had to buy an Airport Extreme card and install it into my PowerMac G4 MDD in order to have it run wireless.
The Airport Extreme Base Station is a router used to connect your computer(s) to the internet via a Cable/DSL modem.
Will the extreme card ONLY work with the Express or Extreme Base station? I have a original one - that went with my original card. Now have a different computer and an extreme card installed - wondering if I can still use the same Base.