A: MED-V is useful not only for running applications that won't work on Windows 7, but also to keep access to IE 6. If you have automatic updates enabled, IE 8 will automatically push down and replace IE 6, which you obviously don't want to happen. The solution is to use the IE 7 blocker tool and IE 8 blocker tool. These downloads have commands to run and templates for blocking via Group Policy.
In my environment, I created an OU for the MED-V machines and applied a Group Policy Object to this OU that had the group policy templates provided to block IE7 and IE8 and just enabled the block policy there.