Sometimes Windows XP or your Toughbook's wireless network connection won't even list a network to connect to. First thing to check is that it is not turned off, either by the physical switch (inside the door on the front left), or by right-clicking on the software switch in the Windows XP system tray show below:
Also, in the picture above there is a white-colored Intel wifi icon. If you are using the Intel software to manage your wireless connections, open it and press F10 to let Windows manage your WiFi instead.
Windows XP Wireless Cleanup
If the WiFi radio is on and you can see the wireless network but it just won't connect, then you need to delete all the preferred networks from the list and then retry connecting.
Right-click on Wireless Network Connection then select Properties.
Click on the Wireless Networks tab. Remove ALL entries that are listed under the Preferred networks category by clicking Remove on each one.