XP Networking Problem

A few days ago I got hit by one of the variations of the Blaster worm. I was able to stay online long enough to download the latest patches from the windows homepage, and thus thought that would be the end of my problem. I installed an even better anti-virus software I just bought since the old one didn't seem to catch blaster.

The problem, however, is that my housemate connects to the internet through my computer using a LAN hub. In the off chance that he got it, we made sure to run extensive scans on his computer, to which turned up with nothing. The problem is that now it won't let him gain access to the internet and we've tried everything; reinstalling network properties, disabling NetBios, etc, and still it won't let him gain access.

Does anyone have any clue as to how this is repairable?