While it doesn't always work, try using Microsoft Update to determine the brand/model of your Wireless networking card. In addition, Microsoft Update may make a recommendation for a driver. However, I tend to shy away from Microsoft recommendations, especially with my recent encounters.
Once again, I must emphasize that you have to use Microsoft Update when attempting this. Windows Update (which comes standard with XP) will not automatically check your hardware for drivers. The easiest way to access Microsoft Update is to visit the Windows Update website, then select the "Microsoft Update" option near the top of the page (I believe the link is on the left side).
Not sure if it will work, yet if it does, should get you closer to finding a driver.