Another fairly easy option, since the computers have Win7 Pro, is for one of the physicians to always use Virtual PC and XP with a copy of AC linked to the "other database" (which would be the one you suggest putting on WHS.)
The only issue is that they would have to make sure which "world" they are in, the Virtual PC, or the main desktop world.
Virtual PC is already (or can easily and legally be) installed with Win XP. It will connect to the network easily and should be a fairly straightforward solution. Did I mention it was Free!
