From what I understand, as long as you've upgraded legitimately from a previous Windows version to Windows 10 using the upgrade offer program then your machines configuration gets whitelsited on the Microsoft activation servers. Keys aren't important in this regard. You could use a generic Windows 10 key to perform a clean install, but when it comes to activating your copy, as long as it recognises your machine as being whitelisted, your copy will be activated. Of course, if you change your PCs hardware it may not activate.