If you're familiar with wireless networks, the information in the "Summary" section is probably sufficient; if not, go to the Table of Contents below and find the section that matches your device's operating system.
Check Specify Authentication mode and choose User Authentication.
Click OK to close Middlebury College Wireless Network properties.
If that does not help, then consider uninstalling the Wi Fi netcard.
Also, make sure that you are using WPA(2) Personal (PSK) for both the Comcast gateway, and for the Wi Fi client that you are setting up; don't try to use "WPA-Enterprise" or "802.1X" security because that almost certainly will require resources that you don't have (resources such as a security certificate for that connection).
Unfortunately, many network cards and/or drivers from the Win XP era do not play well with WPA/WPA2 networks; connecting may require experimentation, patience, and/or cursing, or it may not be possible with your hardware. (SP2 with WPA updates supposedly will do the trick, but SP3 is a good idea anyway.) The exact interface depends on the software you're using to manage wireless network connections; refer to the summary at the top of this document and the help pages or other documentation for your computer.