Need help connecting Macbook Pro to xbox 360

I live in a dorm at college and therefore use the schools network for internet use. I want to connect to xbox live, so i told by the tech-center to buy to cables to do so: a "USB to 10/100Mbps Adapter" and a "Crossover Network Cable"

After i bought them i was told i need to install Microsoft onto my Mac, bc mac does not allow network sharing (something like that).

I considered buying a wireless router, but the guy at the tech-center told me they are not allowed and will be blocked.

Has anyone had this same problem? I like Mac OS X and i don't want to buy and install Microsoft. Is there any possible solution to hook up my xbox 360 to the network? I don't know much about Macs or computers in general so please explain any solutions thoroughly (if there is a solution). Thanks!