How to connect iTunes on Windows to only a specific AppleTV when several are available? We're a college campus that has an iPod Touch program... all new full time students get an iPod when they first arrive on campus. We also have a number of faculty using iPads.

To help take better advantage of these devices, we are about to connect AppleTVs to a number of the projectors in different classrooms... 18 in all. These classrooms also have Windows PCs (mostly XP, but some 7) connected to the projectors.  

What I want to do is install iTunes on each classroom computer, and set iTunes to connect to the AppleTV in that classroom (and only the AppleTV in the classroom). I want it to ignore the AppleTVs from other classrooms.  All the classrooms are on the same subnet.  The idea is that when different faculty members or students log in to the computer with their own profiles, that iTunes profile will automatically see the right AppleTV, and no one will accidentally connect to an AppleTV in a different classroom.

So far, the only way I can see to do this is let the computers connect to any AppleTV they see, and then put each classroom on an individual subnet (a huge pain in the you know what).  Are there any other ideas? I'm okay with hand editing a config file somewhere, if need be.

Never mind that the computer is already connected directly to the projector, and therefore should never need to rely on the AppleTV to show anything in iTunes. If someone tries to use iTunes to control the AppleTV, it should work.
I would suggest, assuming the main function you'll be using is AirPlay, that you give each classroom's Apple TV its own AirPlay password that only the instructor in that room knows. That way, he/she can connect to it with the credentials you've given and no one else can. If a student needs to connect to it to show something, the instructor could put in the password on the student's laptop. Obviously, if the password gets leaked you can change it at will.

I know this seems a little tedious, but I think it's the only way of doing it short of re-subnetting the building (I understand why you'd want to NOT do that!).

Also, I would suggest you create DHCP reservations for each Apple TV on your DHCP server so they always get the same IP address when connecting, just in case your network gets overloaded. Just a suggestion.

Hope this helps a little. Good luck.