Microsoft have confirmed that Windows 10 will only be made available as an upgrade to Windows 7 or 8.1xx until the 29th July 2016.

Users of Windows 7 or 8.1xx are advised to make sure their device is compatible with Windows 10 before upgrading. That said, you will still have the option to roll back to the previous version of Windows for up to 1 month following the upgrade. It is not possible to rollback after the 1 month period has completed and a return to Windows 7 or 8.1xx would only then be possible via a full system recovery or original Microsoft Windows DVD.