Prerequisites : *Microsoft(Outlook) Account signed-in on the PC. *TeamViewer installed(latest version is preferred).
*Activation only for Pro/Home/Enterprise version of Windows. Keep the version installed on which you want activation.
Note : BACKUP your important files from C: drive(Downlods/Documents/Pictures, etc folders) to any other drive D:/E: (in case you need to format).
activation is needed to be done only once, it binds to
your Microsoft Account and so whenever you format/clean-install new
version of Windows 10, it will automatically activate Windows once you
sign in with your Microsoft Account.