Booting a Bootable Windows 10 USB Hard Disk Drive when connected to a USB port of a  PC/Desktop or when connected to a USB port of a Laptop or when connected to a USB port of a  Tablet, for the purpose of trouble-shooting ,  backup/restore, etc., etc., is simply not straight forward . It is not simply connecting a   [ Bootable Windows 10 USB Hard Disk Drive ]   to a USB port of a  PC/Desktop or a Laptop or a Tablet and switch on the power , and automatically the Windows 10 Operating System will boot up . No! It is not as easy as that!  We have to play around with the BIOS/UEFI  settings , like for example      "IDE" ,  "UEFI"  , "USB Hard Disk" ,  "Hard Disk" , etc., etc., of the PC/Desktop or the Laptop or the Tablet or the Engineering Workstation . The  BIOS/UEFI  of the PC/Desktop or the Laptop or the Tablet or the Engineering Workstation have to be setup properly , in order for the  Windows 10 Operating System to boot up properly from the   [ Bootable Windows 10 USB Hard Disk Drive ].