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I want to install Windows 7 on an external hard drive, and boot from it when needed.

Is this possible on a Mac? I have heard from some sources that it is not possible to boot Windows from external drives, at least on the new Macs. I found this quite surprising.

Any idea if this is true?

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possible duplicate of Boot Macbook pro from external harddisk – jtbandes Apr 18 '12 at 15:32
apparently rEFIt doesnt work ... – Newton Apr 19 '12 at 9:40
Doesn't work for what? I've used it to triple-boot before... – jtbandes Apr 19 '12 at 11:25
from an external? what Mac were you using and what OS did it have installed? – Newton Apr 19 '12 at 12:38
Ah no, just internal, sorry... – jtbandes Apr 19 '12 at 12:43

It is possible, but it's not straight forward. This detailed step by step guide (which I did) contains all you need to know to install and run Windows 7 or 8 from an external drive (USB3 or thunderbolt):

To sum up, this guide will help you:

  • Get the Windows installation pack from a DVD or ISO file
  • Partition and format your external drive to make it bootable
  • Deploy Windows on your external drive
  • Boot on your external drive
  • Install Windows
  • Download and install the bootcamp drivers (without even using the bootcamp assistant)
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Could you please summarize the information here and not just give a link. See these meta questions and here – Mark Feb 4 '13 at 13:51
Sorry, I added a summary now. Is it sufficient? – BleepToBleep Feb 4 '13 at 14:26
Hey, please anybody could confirm if it is working ? P.S.: my setup : MBA 2013 + 2 TB WD USB3 External(having 4 partitions 1st NTFS and rest 3 exFAT) – jeet.chanchawat May 10 '14 at 21:02

Bootcamp simply isn't designed to install Windows on an external drive.

7. If I have more than one hard drive, can I install Microsoft Windows on any drive?

You can use Boot Camp to install Windows on any internal hard drive, but not on an external hard drive.

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There is always the possibility to run Windows 7 as a virtual image (e.g. VMWare, VirtualBox). Works well from an external drive and has the advantage that you can start the image from any computer that has the software installed.

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Silly as I am I wanted to do the same a few weeks ago. But the Windows 7 installer told me that it can't be installed on an external (USB or Firewire) drive.

You could probably installed a Windows PE version. But since that's not the Real Deal it wasn't an option for me.

Update There's a How-To Install Windows 7 on an external drive which I gonna try in the next few days. Not sure if that's gonna work on a Mac.

Update 2 I tried to install Windows 7 on an external USB drive following the How-To in the first Update. Unfortuantely I didn't get it to work. Getting it copied to the external drive worked well but after rebooting I got an error about not finding this Windows installation.

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for straightforward-method, you can install and run a bootcamp Windows on thunderbolt drive

Bootcamp Windows does not support for usb and firewire external drive, but do support for thunderbolt drive

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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

Could you elaborate on how Bootcamp runs on an external drive. The official instructions explain this is not only not supported, but not achievable without modifying the code or the install steps. – bmike Feb 26 '14 at 14:44

I have followed BleepToBleep's instruction but couldn't get Windows 7 to boot on external hard drive. It supposed-to-be-bootable hard drive failed to start Windows installation after showing the Windows logo.

So I tried other method and succeeded.

Here is the link: How to install Windows on external hard drive

To sum it up:

  1. Download and install WinToUSB app on a PC or virtual PC.

  2. Partition the external hard drive to have 2 partitions:(similar to BleepToBleep)

    1st partition: 350MB FAT32

    2nd partition: The rest of the hard drive in NTFS

  3. Run WinToUSB with the ISO file of Windows 7 or any Windows

  4. ReBoot the Mac and hold Alt button, boot into Windows and finish the installation. Every times it restarts, hold Alt button and boot into Windows again until the installation finishes.

  5. Download the driver to the Mac.

    If it can be easily found in this link Apple Bootcamp drivers

    If it cannot be found, follow this manual instruction to find. (It will take some time)

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I tried this method and got stuck when I first booted using the Alt button and then choosing Windows: after a minute of showing intensive activity accessing my SSD attached with a USB3 adapter, the Windows boot logo appeared for about a minute and then I was greeted with BSOD (0x7B). – Henno May 11 at 18:44
@Henno what is the spec of your Mac? Mine is MacBookPro Retina 15-inch Mid 2014, core i7 2.5 Ghz, 16 GB of 1600 Mhz DDR3. Also what is the Windows version that you tried to install? I notice that Windows 7 may have some issues with USB 3 so I tried Windows 8 – Leon Nguyen May 12 at 4:48

I have created a detailed guide here:

It will work for any Mac, but especially with retina and air users who are having trouble getting other methods to work

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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

Welcome to Ask Different! While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. – grgarside Feb 13 '14 at 16:35
Kevin can you help me with your tutorial. I dont know what the Silver partition is for i have a 1tb external hdd i want to have windows on and a usb key with windows. So i can't find out what the silver partition is for?. – user71511 Feb 26 '14 at 14:22

protected by bmike Feb 26 '14 at 14:45

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