Two disks are backed up when doing a system backup. One disk is Win7, the other is Win10. Win 7 is the system disk. However, the goal is to backup Win10 only. Disconnecting the Win7 disk, the Win10 does not boot, therefore, does not change to become the system disk to image. Apparently it is missing the MBR. Exactly, how is this corrected so that a system backup of the Win10 disk can be executed?