I assume that's one of the things tested before any release is made.
It would be pretty easy to set up automation to have a bunch of disk image of old copies of windows (both clean copies, and customers disk images full of installed applications and upgraded many times), and then automatically upgrade them to the newest release and run all the integration tests to check everything still works.
It would be pretty easy to set up automation to have a bunch of disk image of old copies of windows (both clean copies, and customers disk images full of installed applications and upgraded many times), and then automatically upgrade them to the newest release and run all the integration tests to check everything still works.