If you are in a Dorm room, there is no way you can go about faking its not you. I remember here at my school, your ip was set, but not only that, your complete host name said which building you were and wat room,
something like rm202eXxx room 202 building e xxxx
Even if he buys another computer, rm202e will still be the same. Now if he had plugged his comp on another person's room, then the other person would have been held responsible. As things are now, he cant do anything.
For example, go to
www.samspade.org and put your IP where it says IP WHOIS and see what comes up. First line will show your IP and your HOST name, your HOST name will include your room number or any other sort of identification to your exact location.
The case becomes even worse if your college does like my college. They make you register your MAC address... then, you cant even hide what you are doing even if you go to the library or a friends room.