How to run Boot Camp on External Hard Drive?

That is interesting. Windows, so I've heard, will only install to a newer iMac that has only USB3.0 bolts, by using an external DVD drive only - NOT from an SD or USB Windows installation ISO. The Thunderbolt SSD has to be of an exact chipset also, in order for Windows to "like it" and install/boot to it. Is the SSD TB drive an all-in-one set, or are you using a TB dock with a separate 2.5" SSD ? Windows 7 or 8? Hopefully 7... 🙂

clone your macintosh hd using carbon copy cloner to the ext hd.

boot from to mac osx from the ext drive, start your bootcamp process etc.

erase your mac hd partition from the ext hd. and you'll have your bootcamp windows on the ext hd.

Hi,

It's absolutely possible to run BootCamp from an External Drive (ie : windows installed on an USB drive)

The windows installation program refuses to install itself to an external USB Drive.

That's not a problem, there's a way to install windows installation files on an external USB drive, and once booted from it, Windows will finish to install itself from said drive.

I tested it with Windows 8.1 x64 and it work perfectly from external USB drive!!

here's how to do so :

You will need :

- your windows 8.1 ISO file (choose x64 because Apple Bootcamp tools are meant for x64)

- a running PC (on windows 7 or 8) real or virtualised

- a blank external drive (at least 16GB)

/!\ WHOLE DISK WILL BE ERASED, I cannot be responsible for data loss /!\

this software :

- Apple Bootcamp drivers (obtained from the BootCamp setup)

- Microsoft AIK tool : http://www.microsoft.com/en-US/download/details.aspx?id=5753

- Power Iso (create a virtual drive, unless you're using a Virtualised Window) : http://www.poweriso.com/

If you don't have Windows ISO, you can download a demo there : http://www.microsoft.com/en-us/evalcenter/evaluate-windows-8-1-enterprise

or try windows 10 : http://preview.windows.com/

On your existing PC Setup, do the following steps (each command will be in uppercase to increase readability, type them in lowercase, if there's a space between words, insert a space obviously) :

1 - install Windows AIK, once done navigate to this folder : C:\program files\Windows AIK\Tools\Amd64\

2 - in this folder, move the file imagex.exe to the root folder of your C:\ drive

3 - launch the CMD line tool (clic on the Start menu, in the search bar type CMD, then launch it from the menu)

4 - at the prompt, type DISKPART and hit Return Key

the command line will be like this DISKPART >

5 - type LIST DISK and hit Return Key

It will list each available drive on your PC with a Disk number (DISK 0 ; DISK 1; DISK # ; etc...)

6 - Choose the disk you want your windows 8.1 installed onto and type accordingly SELECT DISK # and hit Return Key

(# being the number of the disk you want to use (ie SELECT DISK 2) and hit Return Key (according to our example the prompt will state that disk 2 is now the selected disk). Just to be sure of what you did, you can type LIST DISK again, and you will see a * in front of the disk you will erase and prepare for the installation of windows. If you want to be absolutely sure that you selected the right disk, you can unplug the disk and type LIST DISK again and repeat the above steps.

7 - Type CLEAN and hit Return Key

DiskPart succeeded in cleaning the disk

8 - Type CREATE PARTITION 1 and hit Return Key

DiskPart succeeded in creating the specified partition

9 - Type SELECT PARTITION 1 and hit Return Key

Partition 1 is now the selected partition

10 - Type ACTIVE and hit Return Key

DiskPart marked the current partition as active

11 - Type FORMAT FS=NTFS QUICK and hit Return Key

DiskPart successfully formatted the volume

12 - Type ASSIGN and hit Return Key

DiskPart successfully assigned the drive letter or mount point

13 -Type EXIT and hit Return Key or close the window

Following 14 to 16 steps will allow you to have the window 8 ISO mounted as a drive. If you are doing this with Parallels Desktop or VMWare fusion, just mount the .iso file as a drive in the CD/DVD Drive section of the software and go to step 17

14 - Install PowerISO

15 - Clic on the "Mount button", and select "Set Number of Drives Menu", choose "1 Drive"

16 - Then clic on the "Mount button" again, then "Mount Image". Select your windows 8.1 ISO file and clic "Open"

Following steps are for everyone

Please note your drives letters before proceeding :

What is your Windows CD drive Letter ? My Windows Drive letter is E:

What is your external Hard drive letter ? My USB Drive letter is G:

So remember to change the letters for your system accordingly.

17 - Verify that your Window installation drive is properly mounted : clic on the Start menu then Computer, then check the drives (in my case, my Virtual CD Drive is the letter E:)

18 - Open CMD tool again, but this time as an Administrator : clic on the Start menu, then in the search bar type CMD, then right-clic on it in the menu and select Run as Administrator

19 - Type C:\IMAGEX.EXE /APPLY E:\sources\install.wim 1 G:\and hit Return Key(remember to change the letters to fit your setup)

there's several spaces in the above command ligne.

You'll see the ImageX Tool for Windows running, with a percentage [ X% ] Applying progress. It'll take 8 to 12 minutes to complete.

20 - Now we'll make the USB Drive Bootable. Type BCDBOOT G:\WINDOWS /S G:

Boot files successfully created

You're Done !!

Now, plug the USB Drive to your Mac. Start it and hold the ALT Key, and choose the Windows USB Drive that you used all along.

Windows will boot, and then will reboot the computer. at the boot chime hold ALT key and again choose the Windows drive to boot from.

Once on the Windows desktop appears, plug your Apple Windows Drivers USB keydrive and install the Bootcamp drivers.

After a while, the installation will be done, you just have to reboot Windows, hold ALT again at startup to choose the Windows drive, and voilà !

You just completed the installation of Windows on an external drive, and you can boot it whenever you want. The best part of this is that you can use your Windows USB Drive only when you want to use Windows, and free all that space from your internal Hard drive.

You're Welcome

Hi Pierre.

It's a great guide you have created, and i have followed step-by-step, to have Win7 on an external USB3 disk to my Mac Mini.

But every time i try to boot up on the Win7 disk, it just says Windows is starting and then it is blue screening!

I don't know what i've done wrong, have you heard of anyone with issues like this?

Kind Regards

Pierre Nummelin

PS. i'm a brand new MAC user, and i'ed rather not mess up my new MAC Mini with Winows, that's why i'm interested in having it
installed on a seperate disk.

Fuberman,

You won't "mess up your new mac mini with windows" as long as you're using the Boot Camp Assistant. I've done it this way for sooooo many years, mostly because it's the only real option. If you ever want to revert back to your factory hard drive settings, you can undo the boot camp partition with a few clicks and things are back to normal.

On a peripheral note, I'd also not be too keen on running my Windows partition via USB 3.0 even if it were possible simply due to bandwidth. I'd rather use Thunderbolt, again...if it were supported.

A third option depending on how hands on you'd like to get...you could always install a second hard drive in to your mac mini and have it be dedicated to Windows. I've done this with my current model mac mini and it's worked just fine for some time now. If you need help with that, just ask.

Zathrak wrote:

On a peripheral note, I'd also not be too keen on running my Windows partition via USB 3.0 even if it were possible simply due to bandwidth. I'd rather use Thunderbolt, again...if it were supported.

USB3 connections are faster than most internal connections, there no performance issues except Windows reluctance to run from an external drive.

Oh come on... even on USB 2 it's worth it !

The only point of installing Windows on a external drive is because you may need windows from times to times, but you don't want to loose some precious disk space over something you barely use...

so installing Windows on an external drive (even if that's a slow USB 2 Hard drive or even USB Key), is a good way to test Windows software when needed. and beyond slowness, that's the only issue you'll encounter, and you know it in advance : your external windows won't be as fast as if it were installed onto the bootcamp partition on your internal SSD drive... deal with it !

And did I mention that you can this way use the same external Hard drive on several Macs ?

you can use the same Windows on an iMac and a MacBook pro for instance, Windows will add needed drivers, maybe you'll have to reinstall the Apple bootcamp drivers when plugged to another computer, but that's it !!

there's not any downside on doing this !

you can buy a SSD thunderbolt powered drive, yes, you can, but that's up to you and your budget !

To @ Fuberman

I made this guide for Windows 8.1, you should try it with the windows 8.1 test drive ISO available on the Windows website.

you can also give me the BSOD error message you got when booting windows.

maybe it's just nothing.

but just to be sure, try installing windows 8.1 please !

@Pierre80

Thanks for trying helping me out on this one.

I would like to try with Windows 8.1 I'm just not sure if it's possible for me to

use Win8.1 though i'm only have a license key for Win7.

But i will try it out the next couple of days, when the time allows me 🙂

I have just updated to Yosemite, i do not hope that make any difference...

/Pierre

Try this..

http://twocanoes.com/winclone/support/migrate-windows-8-to-an-external-drive-usi ng-winclone-4.3-and-later

It took me 15min to move bootcamp to USB drive and it boots to an external drive now...Just buy winclone for 29$ and save yourself a headache..instruction is on their site and 3 easy step..

1. Plugin external drive and partition it MS-DOS(Fat32)

2. Select Bootcamp partition in Disk utility and migrate bootcamp to external..

3. Reboot by pressing "option" and select external..

Finally , reclaim your extra space anf make your MacintoshHD a single drive again

Now i've had the time to try Pierre80' user guide again with Win8.1 and i guess i took me around 30 - 45 min and then everything

works smooth, rebooting from external USB3 disk, and no Windows installed to the Mac 🙂

And best of all...it's for free 😉

So i can only recommend this guide, just be aware, Windows have to be 8.1.

✌️ I'm glad that my guide worked for you, and you're right, it's free

feel free to mark my guide as a solution or grant me points

hi am a newbie here ... can i know the total size needed for installation on the USB 3 drive? intend to try pierre80's guide because i do not want to waste precious space on something i will only use rarely. tq

Mac OS Yosemite and Win8.1 on external Thunderbolt/USB 3 drive.

How to:

Remember before you start: Make sure you have updated backups on everything involved, unmount all not necessary drives. during the different stages unmount the drive not working on i.e. if you are doing things on the external unmount the internal. Take your time and be sure to choose the right drive and partition so you don’t mess everything up.

1. Update all Mac OS updates from Mac App Store.

2. Run Boot Camp on internal (original) drive, including make a USB stick drivers for Win (Can take forever on a slow USB stick, but will get there) Install Windows from DVD or similar (I did from a bought DVD, no OEM allowed)

3. Test-run and configure and add all updates for Windows and installing an Antivirus app is also good to do.

4. Install a new fresh Mac OS on an external USB or Thunderbolt drive (or use CarbonCopyCloner to get a copy of internal Mac OS)

5. Check the new external Mac OS by rebooting to it. if Ok, reboot to internal again.

6. Run WinClone 4 and make an image file from the Boot Camp to an image file to your desktop.

7. Run Disk Utility and select your external drive, Choose the Partition tab, click the + below the main (only partition), select the space between the now two partitions and drag upp or down until lower parts size is at least a tad bigger than the original Boot Camp volume or bigger. Select the new partition and rename it and choose to format it to MS-DOS FAT. Execute.

8. Run WinClone again and choose your new image-file, and target your new FAT-partition on the external drive.

9. Reboot the Mac, and when screen goes black, press and hold the alt-button until the startup drives is shown, select the new Windows disk on your external drive. If all ok your computer will start on Windows on your external drive. When running Windows goto your USB-stick open the Boot Camp folder and run the setup.exe.

When all seems to work ok reboot again and this time to your internal Mac OS.

10. When in your internal Mac OS, run the Boot Camp app again and make sure only the Remove Win8xx is checked, run and the Boot Camp will be removed on your Mac drive.

Check-run everything agan.

Thats how I did it, might be easier way but at least I’m a happy camper now :-)

So now I have the options to run Mac OS on my internal drive, run Mac OS on my external together with Parallels Desktop and Windows 8.1 in a virtual or just run Windows only on the external drive (best for gaming etc in windows)

Hi, I'm trying to run windows off of an external hard drive because I ran out of space on my internal and can't delete stuff (I need it all).

I followed your directions using a boot camp created install USB stick as my iso source. Everything worked, except that I had to type 'create partition primary' at step 8 instead of 'create partition 1'. After I finished all of the setup, I went to boot up my MacBook Pro from the external hard drive, but I got the "boot files are missing or corrupted" error message (not exact quote; for obvious reasons I don't have a screen shot). When this happens to "actual" windows users, they load in the install source and boot from that, then click repair. I did that, but it only gave me the option to install windows on my various partitions; as far as Setup was concerned, there was no windows install to fix. I then plugged the hard drive back into the windows machine and did the boot files transfer again, but I got the same results. Your directions expected windows to simply reboot after the first time, but it never tried that. What is going on?

Hardware: 2014 MacBook Pro Retina, i7 chip

WD Elements 1 TB 7200 RPM external HD (USB 3.0)