

So, if you own a new computer with Windows 10 preinstalled and you have already activated Windows, you don't need to know the product key in order to re-install Windows 10, because the Activation status is stored on Microsoft's servers, and after the installation, Windows 10 will be activated automatically by using the information from MS Servers.

Today – fortunately – Microsoft gives the ability to clean install Windows 10 on your system by using a valid Windows 7, 8 or 8.1 key without having to update your system to Windows 10 first. In the past if you own a Windows 7, 8 or 8.1 based computer the only way to perform a clean install of Windows 10 on your PC is to update first your system to Windows 10, by using the 'Windows Update Assistant' and after activating your copy, to perform a clean installation. To perform a fresh install of Windows 10 on your computer you must own a valid Windows 10, 8.1, 8 or 7 key to activate your copy, or an already installed and activated version of Windows 10, 7 or 8/8.1 OS on your system. This tutorial contains detailed instructions on how to perform a clean Windows 10 installation from USB on your computer.
