Quick guide to install Windows 8.1 (UEFI) in external USB/TB drive

Discussion in 'Windows, Linux & Others on the Mac' started by yjchua95, Dec 20, 2014.

  1. yjchua95, Dec 20, 2014
    Last edited: Dec 21, 2014

    yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    Hello all,

    Just a quick guide for some people who may want to install Windows in an external drive (USB/TB) in a UEFI environment.

    Note: The drive enclosure should support UASP.

    Connect external drive to a Windows VM. You must have a Windows VM in VMware/Parallels.

    What you need:
    install.wim file (obtain this from your Windows ISO)

    Open elevated cmd.exe

    Note: All commands aren't case sensitive, including pathway to files.

    Type diskpart
    Type list disk
    Take note of the disk you want to select
    Type select disk 1 (if your disk is Disk 1)
    Type clean
    Type convert gpt
    Type create partition EFI size=100
    Type format quick fs=fat32 label=EFI
    Type assign letter=S
    Type create partition primary
    Type format fs=ntfs quick label=W2G (or any other name you wish for label)
    Type assign letter=E
    Type exit

    Open up File Explorer. In your C drive, create a new folder named WIN2GO.
    Put the install.wim file in this folder

    Back in cmd.exe:
    Type dism /apply-image /imagefile:C:\WIN2GO\install.wim /index:1 /applydir:E:\ (this process will take quite a while)
    Type E:\Windows\System32\bcdboot E:\Windows /s S: /f UEFI

    Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot.

    Proceed installation normally.

    After installation, install Boot Camp drivers.

    Hope it helps.

    Note: If you have an install.esd file instead of install.wim, follow the guide here to convert it into a .wim file.

  2. Gjwilly macrumors 68030

    May 1, 2011
    SF Bay Area
    Once you've successfully created the bootable external drive can you take that same drive to an other Mac that doesn't have and never did have the virtual Windows machine?
  3. UniDoubleU macrumors regular


    Aug 14, 2014
    Yep, I've used this method for 8.1 and it worked perfectly. I'm not sure if I'll have to do it for a clean install of Win 10?

    Assuming the other computer is not of the same model I think you might have problems with driver conflicts.

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