Easy to find via regedit, the windows 10 serial numer activation key is not magic anymore. Although the key ideally should be encrypted and not stored as plain text, the windows 10 activation key serial number is stored as a plain text string.
The windows 10 activation key serial number can be found in windows 10 registry under HKLM\SOFTWARE\Microsoft\Windows NT\SoftwarerotectionPlatform.
While changing the windows 10 activation key serial number in the registry is not the best way to do it, this registry is still the best way of finding the windows 10 serial number activation key. While this is the place to find the windows 10 activcation key serial number, it might be the same place for older versions of windows. You could search for windows 8 serial number or windows 7 activation key serial number and see if it is in the same place. Let us know if you find it in the same place as we found windows 10 serial number activation key.
While the Windows 10 product key can be found in the system info page (click win + break to see it ), the windoes 10 serial number might be more interesting and this one can only be found in the registry.
You can also press the win key and type info then open the first suggested page and that will display the information page for your computer. Although this shows some more info, including the product ID, the windows 10 activation code can only be found in the regsitry.