It's quite easy to share internet connections between your laptop and Xbox, and it works the charm without any mods. However, it may not be an enabled/available option on that connection. Check around in your Window's "master settings" so to speak, to see if there's anything hiding the option.

I personally bought a Wireless G Official Xbox Adapter. It works fine, and once configured on the Xbox, works for all devices with an ethernet port. From my room (2nd floor, location of the modem/Linksys G router) to the basement (location of Xbox, Wireless adapter) I get a varying signal from about 2 MBPS - 18 MBPS.