have a look at the range of products on the apple website-
http://store.apple.com/Apple/WebObje...irportwireless
If your lappy is airport enabled then the airport card is the best way to go- unclip the keyboard and it will be obvious how it is installed.
If not then that page above shows the PC card or USB options available- I wouldn't recommend buying non-apple items from the apple store, because you can find them cheaper elsewhere, but at least it will give you an idea of what is definately compatible
