UltraVNC works with Vista. We had some problems at the school I work in, though. It froze constantly, meaning you had to then walk out to the computer to finish the job. By which time, kids could have messed about with stuff and it would take you longer.
However, I don't know whether or not that issue has now been resolved.
Your IT department probably uses a form of VNC. There are a few out there that are half-decent, you just need to do some research.