With Windows 10, Microsoft introduced a new activation system called digital entitlement that allows users to upgrade from an older operating system, such as Windows 7 and 8.1, to the new one without the need for a product key.
Once the upgrade is complete, the system automatically activates (assuming you were running a genuine version of Windows 7 or 8.1), with Microsoft then allowing you to clean-install without asking for a product key anymore.
Windows 10 is re-activated every time you reinstall thanks to this digital entitlement system that attaches a product key to your system (manual re-activation is needed when you make significant changes to your PC configuration, such as replacing the motherboard).
In an updated article in the Windows 10 FAQ
, Microsoft details the scenarios when you need a product key for the new OS and when you don't, explaining, however, that all users upgrading from an older version do not need one.
Basically, the digital entitlement system works in four different cases, as follows:
|You upgraded to Windows 10 for free from an eligible device running a genuine copy of Windows 7 or Windows 8.1.
|You bought genuine Windows 10 from the Windows Store and successfully activated Windows 10.
|You bought a Windows 10 Pro upgrade from the Windows Store and successfully activated Windows 10.
|You’re a Windows Insider and upgraded to the newest Windows 10 Insider Preview build on an eligible device that was running an activated previous version of Windows and Windows 10 Preview.
This means that, even if you purchased Windows 10 from the store, you are allowed to clean-install without the need for the product key. You can re-install as many times as you want and re-activation should be performed all automatically.