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yjchua95

macrumors 604
Original poster
Apr 23, 2011
6,725
233
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.

http://www.intowindows.com/how-to-easily-convert-install-esd-to-install-wim/
 
Last edited:
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?
 
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?

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?

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