Here are some articles from one of my favorite networking Web sites about how to get Windows machines working with the Apple AirPort

http://www.practicallynetworked.com/networking/airport_pc_setup.htm
http://www.practicallynetworked.com/networking/airport_pc.htm

Upgrade the Wavelan card found in the AirPort: http://www.msrl.com/airport-gold/ (plenty of other good links on this page as well)

Here's some more software that might help:

FreeBase
Size: 1.4M
OS Support: W9x/NT/2k
Cost: Free
URL: http://freebase.sourceforge.net/

"At US$299, the Apple AirPort Base Station is the cheapest wireless Access Point that complies with the 802.11b wireless networking standard. It comes with an Ethernet port, a V.90 modem and it includes the WaveLan card. Unfortunately, it only comes with configuration software for the Apple Macintosh Operating System. FreeBase was written to allow Windows users to configure the Base Station, and to allow replacing the WaveLan card with a 'WaveLan / Orinoco Gold' card so users can have strong encryption. FreeBase is free software released under the GNU General Public License, and comes with absolutely no warranties of any kind. FreeBase is written in Visual Basic, and the source code is freely available."