Heard this one from a friend who's setting up GNU/Linux systems for schools in Colorado, had a writeup in Wired.

In their case, legacy MS Windows support was still necessary, but admin costs were high. The solution was:
  • Linux desktops running as diskless X clients
  • Linux server, running multiple instances of Lin4Win.
  • User "experience": running Windows from a centrally administered system, with high stability and low costs.
Not sure if this would be satisfactory for you, but it worked well in their case. Contact me for further info.