John wants to upgrade to Windows 10 and he can't find the product key. Leo says that if the computer is already activated, the free Windows 10 will just take that authorization and apply it to his new version of Windows. There's no need to to reactivate or re-enter the license key. Windows will not ask him for it. If he's getting the product key request, then the previous version wasn't activated. But Microsoft has changed the way it licenses Windows now to an entitlement system where his computer is entitled to run Windows 10.