Dell provides firmware updates in form of Windows executables only (in case of my hardware), so I have a need to run Windows 8.1 sometimes only for that.

Howto:
– download WinToUSB
– get Windows 8.1 ISO image
– connect USB HDD drive
– run WinToUSB, point to ISO image, destination drive and install Windows
– boot from USB HDD

That’s all. Works.