After upgrading from Windows 7 Home Premium (OEM) to Windows 10 Home and being automatically activated, I did a clean install of Windows 10 Home and again activated automatically. I did not enter any product keys when asked. If I use Aida64 or a product key viewer I can see a complete product key, in Windows 10 Home. Does anyone know the purpose of this key? I was thinking that the key could be used to activate a clean installation without going online? Most likely only on the same PC? Has anyone tried using this key for activation, say when reinstalling or doing a clean installation on same PC?