Install Windows 10 to External Drive on Macbook

September 15, 2020 · 3 min · 488 words

Having an installation of Windows availiable is often really useful! However, I don’t quite have enough space to dedicate an internal partition on my 2018 MacBook Pro. Instead, I wished to install Windows to an external drive to give me the benefits of having a Windows install without losing storage space for my primary macOS installation.

Disable Secure Boot and Enable Boot to External Drives

Steps widely documented.

Create Windows 10 Installation USB

Using a Windows machine create a Windows 10 installation USB using the Windows 10 installation media creation tool

Installation Steps

  1. Plug the Installation USB into the Mac and turn on. When the Apple logo appears hold down the Option key.

  2. A menu should appear selecting the boot drive. Select “EFI Boot” which represents the Windows 10 Installation USB.

  3. As we don’t have the correct drivers installed yet we will not be able to use the Macbook’s internal WiFi, Keyboard or Trackpad. We must instead plug in a USB mouse and keyboard to use the installation.

  4. Once on the screen with language selection, open the command prompt by pressing SHIFT + F10.

  5. Prepare the destination drive by opening diskpart by running command diskpart:

    1. Select and prepare the drive:
      • list disk
      • select disk X (where X is the id of the external drive)
      • clean (WARNING: This will wipe the drive)
      • convert gpt
    2. Create EFI and MSR partitions:
      • create partition efi size=200
      • format quick fs=fat32
      • assign letter=S
      • create partition msr size=16
    3. Create the primary partition
      1. create partition primary
      2. format quick fs=ntfs
      3. assign letter=W
    4. Exit diskpart: exit

  6. Determine edition to install: dism /get-wiminfo /wimfile:C:\sources\install.esd

    • E.g. Index: 6 for Windows 10 Pro

  7. Install Windows to the drive: dism /apply-image /imagefile:C:\sources\install.esd /index:6 /ApplyDir:W:\ /CheckIntegrity Where /index:6 is the index found in the previous step

  8. Install boot files: bcdboot W:\Windows /s S: /f UEFI

  9. Installation complete! Close the command prompt and close the installer using the X button which will restart the machine.

  10. Hold option when the apple logo appears.

  11. Unplug installation media.

  12. Boot into new installation by selecting “EFI Boot”. The machine may restart a few times on first boot - hold option on Apple logo and select “EFI Boot” on all reboots.

  13. Proceed with first boot configuration steps. Note that you will not be able to connect to the internet using WiFi until drivers have been installed.

Post Installation Steps

Obtain and Install Bootcamp Drivers

  1. Run macOS and start Bootcamp Assistant to obtain Windows drivers.
  2. Select Action > Download Windows Support Software to download drivers.
  3. Open setup.exe under Windows to to install drivers.
  4. Reboot. You should now be able to use your internal keyboard, trackpad and WiFi.

Install Mac Precision Touchpad Drivers

  1. Download from Github
  2. Extract
  3. Right click AmtPtpDevice.inf and click install

Fix The Clock

Windows and macOS store the time on the motherboard in different ways.

  1. Open Registry Editor by typing “regedit” in the Start Menu.
  2. Navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TimeZoneInformation
  3. Create a new DWORD under TimeZoneInformation:
    • Name: RealTimeIsUniversal
    • Value: 1