The product keys for Enterprise editions of those older Windows versions, as well as those from volume licenses or counterfeit copies of Windows, will not work, though. Microsoft notes that product keys for many versions of Windows 7, Windows 8 and Windows 8.1 can be used now, starting with Windows 10, version 1511, which was released as a system update last November. Depending on how you upgraded to Windows 10 and the version you were previously using, you may not need a product key (serial number) to activate Windows 10 again after a clean installation.
What happens if I need to reformat my hard drive and reinstall the operating system? How do I reactivate Windows?Ī. The Windows 10 upgrade is a free download for Windows 7 and Windows 8.1 machines, but it doesn’t seem to have its own serial number and obviously didn’t come with an installation DVD.
