for what it's worth; in previous windows versions applicable [all vista & XP SP3] if you elect not to enter a product key during installation, a key [default] will be automatically entered [differs according to version] and the entered key is used to calculate a product I.D. that is displayed on the my computer/properties page. when & if you choose to change the key [e.g. if you have a legal applicable key] you will find that the product I.D. will change. Don't believe me??? Do an install, don't enter a key and when it finally boots up, run the old jellybean and see what it says.......... Then do a keychange to verify, if you need to......
clarification The default keys [as defined in this thread as the one that's installed if you don't provide one, and present in an unactivated system] for all known editions and even some editions I've never seen mentioned here, are all available in sources\product.ini on the Windows7/Server2008R2 install dvd.