By default, Windows 10 builds are pre-keyed, meaning, you do not have to enter a product key and should not be prompted to enter one even after Windows 10 has completed setup.
Will users who take advantage of the upgrade offer for Windows 10 from Windows 8.1 and Windows 7 also be able to obtain recovery media?
Microsoft recently noted the following options available:
With Windows 10, you can create your own recovery media and back up the pristine state of the operating system and preinstalled software. If things go wrong and you are unable to refresh or reset your device successfully, you
can boot the device using recovery media and reset to the prior pristine state.