Wouldn't turning off file sharing work? When I was in a network like that I had 2 shared folders. One with access for everyone, that was a folder of stuff I wanted to share with people. And another that was password protected for me if I happened to need something while I was at another computer. Most of the other people on my network just had one share, that was they're c drive, with full read-write access (to prove to a friend how stupid this was I changed his backround from the other side of campus). I'm not saying that cleaning up your poser directory is a bad idea though.