How is Boot Camp Useful on an External Hard Drive and How to Run It?

Installing Windows operating system on an external hard drive would be the great solution for disk space problems, especially if you wish to run Windows on your Mac system. But, Boot Camp restricts installation of Windows on an external drive.

However, there are few techniques you can try to install Windows operating system on an external hard drive, like generating clones of current PC, using Microsoft IT programs and more.

But, in this informative blog article, it is illustrated how to install Windows OS on an external hard drive without prior installed Windows PC or virtual environment.

Note: Completely go through the process once, before implementing it. Also, it is suggested make earlier backup of your external hard drive data.

Things You Need to Run Boot Camp on External Hard Drive:

1.     USB flash drive (min 4GB capacity)

2.     Bootable external hard drive

3.     Original Windows 10 ISO or install CD/DVD

4.     Mouse/Keyboard (wired)

5.     Boot Camp Windows Support Software

6.     VirtualBox virtualization app


  1. Erase and Format the External Drive

  • Connect the external hard drive to Mac machine
  • Go to Applications -> Utilities and launch Disk Utility
  • Select the external hard drive and click the Erase button
  • Set the Scheme to Master Boot Record
  • And, Format to MS-DOS (FAT)
  • Name the external hard drive (suggested naming Win10 external)
  • Choose the Erase option
  1. Erase and Format the USB Flash Drive

  • Connect the USB flash drive to the Mac
  • Go to Applications, then Utilities and select Disk Utility
  • Select the USB flash drive and click the Erase button
  • Set Scheme and Format to Master Boot Record and MS-DOS (FAT) respectively
  • Name the USB flash drive
  • Click the Erase option
  1. Get Boot Camp Windows Drivers on USB Flash Drive

  • Navigate to Applications -> Utilities and open Boot Camp Assistant
  • Click the Continue button and in Select Tasks dialogue box
  • Disable “Create a Windows 7 or later version install disk” and “Install Windows 7 or later version” options
  • Enable “Download the latest Windows support software from Apple” option and hit Continue
  • Select the USB flash drive to install Windows support files and click Continue

Now, Boot Camp Assistant installs Windows support software on the USB flash drive. Provide credentials (administrator password) for Boot Camp to change the file permissions on the USB flash drive and hit the Continue button.

Note: Want to “fix disk is unreadable” error on Mac in just a few simple steps? Then, check this page!

Procedure to Install Windows on the External Hard Drive using VirtualBox:

Step 1: Install VirtualBox

  • Download and install VirtualBox
  • Go to Mac Applications, select Utilities then launch Terminal
  • Type diskutil list and press Enter key
  • A list of all attached disks to Mac will be displayed. Find your external hard drive (it should be WIN10 of type DOS_FAT_32). Note down its disk number (Identifier). E.g. disk1, disk2, disk3, etc.
  • Locate the external hard drive on the Desktop/Finder Right-click on it and select Eject option

Step 2: Map External Hard Drive to VirtualBox Disk

  • In the Terminal, type sudo VBoxManage internalcommands createrawvmdk -filename “bootcamp.vmdk” -rawdisk /dev/diskX and hit Enter key
  • Replace X with the actual disk number (disk identifier) of your external hard drive
  • In Terminal, type in your admin password, and press Enter button

Step 3: Create VirtualBox Virtual Machine for Windows

  • In Terminal, type sudo /Applications/; press Enter
  • In the VirtualBox, go to Tools (toolbar) and click on the New button
  • Give a Name for the installation (suggested WIN10), Set Type and Version to Microsoft Windows and Windows 10 (64-bit) correspondingly
  • Click Continue, accept the default memory size and proceed
  • In the Hard Disk dialogue box, choose to Use an existing virtual hard disk file
  • Under, “Use an existing virtual hard disk file” category, click on the folder icon (located at the right of the dropdown menu), browse and select vmdk file (present in home folder), click Open button, then Create
  • In VirtualBox, select your Windows 10 virtual machine, and find your Optical Drive. (typically located under Storage section of the virtual machine)
  • Open the Optical Drive item and select Choose Disk Image
  • Browse and select the Windows 10 ISO image; click Open.

Step 4: Install Windows on External Hard Drive using VirtualBox

  • In the VirtualBox toolbox, click the Start
  • The Windows 10 installation process will begin. Track the on-screen instructions.
  • Go for “Custom: Install Windows only (advanced)” option when prompted that “Which type of installation do you want?
  • The Windows setup displays the available drives and partitions on which Windows can be installed. Select the external hard drive, and click Format
  • After format, click Next. Windows installation process will start
Caution: When computer says, “Windows needs to restart” after the installation process, shut down the Virtual Machine immediately.

Step 5: Reboot Mac with Windows using External Hard Drive

  • Close all running applications and reboot the Mac
  • Hold down the Option key during restart, use arrow keys and select Windows drive (external hard drive)
  • Now, your Mac will boot from the external Windows hard drive
  • Windows may restart Mac during this process. So, while Mac is rebooting, hold down the Option key and select Windows to boot from

Step 6: Tune Apple Hardware to work Under Windows

  • Connect the USB flash drive (used earlier to make the Windows Support software) to Mac
  • Click the Windows Start menu and open File Explorer
  • In File Explorer, select your USB flash drive
  • Double-click on the Boot Camp folder and run the setup file (executable file) present inside it
  • Follow the on-screen instructions and install the Boot Camp drivers.

Once the installation of drivers is completed, all your Apple hardware, such as wireless keyboard, mice, mouse, etc. will work.

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