This is what I say! Change all the OS in everyones computer but mine, baby. I'll stick to XP, NT, whatever, as long as it works with the version of ACAD I have. If I'm a security threat because I'm not using the Vista system then give me a system off the network - Computer A. I'll copy to cd and send them through email this way, from Computer B (with Vista).
Now that creates a purchasing problem for IT. They have to justify why all in the CAD dept need 2 systems, or brunt the cost of ACAD 08 to go with Vista.
Not your problem, not ACAD problem. IT problem!