problem connecting to Airport Extreme from Windows XP laptop

We recently replaced an old D-Link router with an Airport Extreme base station. This has worked fine for our Mac laptops, but not for my roommate's windows laptop (which had no problem connecting to the old network). She's using Windows XP and a D-link AirPlus G card (which is 80211.g compatible). Her computer can see the network and connect to it without any problems. However, it has trouble acquiring an IP address. Most of the time, if I check the connection properties, it says "acuiring IP address" for an indefinite period.

The one time I was able to get a viable IP address, I was still unable to connect to the internet, despite a) a strong signal (the laptop was practically on top of the base station) and b) I was able to connect fine with my Mac laptop at the same time

Todd