A: If you upgraded your Windows Phone 8.1 device to Windows 10 Mobile, you can use the Windows Device Recovery Tool to rollback to a previous version. For more info about this tool, see Windows Device Recovery Tool: FAQ .
Report abuse. Hi, Once a Windows key is used on a certain machine, it will be permanent on that specific machine. Windows 8.1 can no longer be used to upgrade your computer to Windows 10. The Windows 10 free upgrade through the Get Windows 10 (GWX) app ended on July 29, 2016. Creating an installation media is only allowed once you already have
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