On the enterprise version of windows there used to be a Windows to go feature that allowed you to install Windows on an external hard drive or Flash drive. Unfortunately since Windows 10 Version 1903 the feature has been deprecated.
Solution 1
So if you have an older instillation disk of windows 7 / 8.1 / 10 (Prior to Ver 1903) Enterprise Edition install it on a fresh dedicated machine (With no internet so it does not upgrade) and use the to go feature to create an External Windows Bootable HardDrive. If you don’t have a dedicated machine install Windows 10 Enterprise on a Virtual Machine like VM Ware or Hyper V and use it to create the external Bootable Hard Drive.
Solution 2
Again I recommend using a fresh copy of windows, then use a hard drive cloning software like AOMEi to clone the hard and make it bootable. I am sure othe cloning software like Acronis, Clonezilla, or Paragon Hard Disk Manager will also do the trick.
