New
#71
The activation is in most cases an upgrade, with the upgrade the hardware of the user is registered on the servers of Microsoft. This registration is called a digital entitlement. When you perform a reinstallation Windows checks the servers of Microsoft to see if any digital entitlement is present and if the right OS is installed that is with the digital entitlement, if all is fine Windows is activated without entering a key. This all makes that you can reinstall Windows an infinity amount without any activation issues :)
BUT, when a motherboard is changed it is seen as a new system and then you have to input a key when installing.