I recently upgraded to Windows 10 with the help of the installer provided on the website. It upgraded my Windows 8.1 single language to Windows 10 Home single language, but Windows has not been activated. It gives me the following error:
"Activation failed because this device doesn't have a valid digital entitlement or product key. Error code: 0x803F7001"
I tried entering my Windows 8.1 product key but it shows that the key is being used by another PC (which is not true !)
My Windows was activated before the upgrade with a legitimate product key and I didn't do a clean install then why isn't it activating ? Wasn't it supposed to be a "free" upgrade ?