New
#11
what an intriguing question! since you were using the name, i figured you could intentionally screw up netbios name resolution by adding your roomate's computer name to your LMHOSTS file and pointing it to 127.0.0.1... however, in my tests, it didn't matter. besides, this wouldn't help you if he connected based on your IP address.
if you control your router that your roommate connects to, and he doesn't have your password, you can set a DHCP reservation for his MAC address. then, set it to some IP that you'd block in your firewall. but if he knows networking, all he'd have to do is statically set an address on his box... if you had some super funky subnet mask, it would be harder for him to guess at a valid address, but even that's a long shot.
i was also going to suggest using ARP to force his MAC address to go to an invalid address on your PC (to intentionally confuse networking), but the problem is that you can have a single MAC pointing to multiple addresses. even if you delete the current instance, once you do any netbios broadcast, your ARP table gets rebuilt.
if there were a firewall app you could download that could block based on a MAC, you'd be set.