Could you go to Settings > Update & Security > Activation and verify the status of your edition of Windows? If it is indeed "Expired", then the only acceptable solution is to purchase a license from Microsoft.
If you have a legitimate copy of a previous version of Windows 7, then you may rollback to that edition, enter the valid product key that you purchased for Windows 7 and then upgrade back to Windows 10.
You would need a Windows Central account to provide us with additional information or to ask further questions in this thread.
08-11-2015 04:53 AM