Ok, but what about this:
XP Professional with a multiple use key (for say, a college computer lab where all the computers have the same XP key on them).
We put Windows 7 upgrade disk on ONE of those systems to test it out and see how it runs. It wipes XP out on that disk and does a clean install, fine.
However, will 7 deactivate that XP license? If we need to install XP on a new computer we build, using our "lab" key, will we run into trouble? I don't want an entire lab's XP key to be "killed" and no longer able to be used because we put Win 7 on one machine.