Please Help: Trying to run Windows 8.1 Pro on external SSD

Discussion in 'Windows, Linux & Others on the Mac' started by fav, Apr 26, 2015.

  1. fav, Apr 26, 2015
    Last edited: Apr 26, 2015

    fav macrumors member

    Jul 3, 2013
    Hi, I have MBPr 2014 15" and trying to run Windows 8.1 on external SSD. I followed this guide.
    Installation is completed, but when I boot the windows, it keeps loading forever. While I was installing, I made 2 mistakes.
    1) I made the installation usb flash by using 8.1 Pro, but I had to get "install.wim" from 8.1 Enterprise demo. I had to format entire flash drive on MBPr to make a partition to install 8.1Pro, then I forgot to move ISO to External HDD, so it's gone. I have a disk, but my CD drive is broken that time, so I decided to download a demo to pick install.wim.
    2) After the installation was done, and opened the disk image into the external SSD, I erased the partition on MBPr's flash storage. Some other sites say I had to keep the partition somehow.

    Do you think these are causing the problem, or am I missing something?

    Thank you, and sorry about my terrible English.
  2. yjchua95, Apr 26, 2015
    Last edited: May 2, 2015

    yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    That website only works if you're using a non-UEFI 2.0 Mac (Ivy Bridge and earlier Macs).

    Here's how (includes methods for both non-UEFI and UEFI). In your case, use the UEFI methods.

    Connect external drive to Windows VM. You must have a Windows VM in VMware/Parallels/VBox, or a Windows PC. Any existing Windows environment will do.

    Note: If you’re using a 32-bit ISO, your Windows environment used to do these commands have to be 32-bit. And if it’s a 64-bit ISO, the environment has to be 64-bit.

    What you need:
    install.wim file (obtain this from your Windows ISO)

    Open elevated cmd.exe (run as admin)

    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 (do this and then stop at this point if you're using a drive with a Thunderbolt port. If installing in BIOS-CSM, type convert mbr and then stop at this point if you’re using a drive with a Thunderbolt port)
    Type create partition EFI size=100 (skip if installing in BIOS-CSM)
    Type format quick fs=fat32 label=EFI (skip if installing in BIOS-CSM)
    Type assign letter=S (skip if installing in BIOS-CSM)
    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 (use this one for UEFI installation)
    Type E:\Windows\System32\bcdboot E:\Windows /s E: /f ALL (use this one for BIOS-CSM installation)

    Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot (or whatever else that comes up for a BIOS-CSM installation).

    Proceed installation normally.

    After installation, install Boot Camp drivers. Feel free to trash the VM once you're done too.

    For best results, use USB 3/Thunderbolt. If you don't have USB 3, use Thunderbolt. If you have neither, stick back to the internal drive :)

    Don’t use a USB stick.

    Note: This method involves reformatting the entire external drive.

    For Thunderbolt drives, just boot from the Windows USB installer and install directly onto the TB drive. Windows sees TB drives as an internal PCIe connection. However, you must format the TB drive as GPT first.

    CAUTION: Windows can only be installed in UEFI flawlessly on Haswell Macs and later. Ivy Bridge and earlier Macs can only run Windows in BIOS-CSM flawlessly. Attempts to boot a UEFI installation of Windows on an Ivy Bridge or earlier Mac will result in driver issues.

    These steps do not work with Windows 7, as it lacks the dism.exe utility.

    UEFI-compatible Macs:
    MacBook Air (mid-2013 and later)
    iMac (late-2013 and later)
    Retina MacBook Pro (late-2013 and later)
    Mac Pro (trashcan shape)
    Mac Mini (late-2014 and later)

    Non-retina MBPs, along with other Macs not listed above (basically all Ivy Bridge and older Macs), are not UEFI compatible.

    WinToUSB basically does the same thing, but doesn’t always work because WinToUSB doesn’t really take into account between BIOS-CSM and UEFI Macs; it only uses one method for all (which may result in boot failures and other problems).

    Edit: Updated to take into account between MBR and GPT.
  3. UKgaryb macrumors regular

    Dec 13, 2013
    Manchester, UK
    Do you have access to Windows 8.1 Enterprise? I do exactly this:

    I've got a Visiontek USB 3.0 mSATA Enclosure + Crucial M550 256GB mSata SSD
    Running Windows 8.1 on it.

    I use it for Steam + Games and it's ultra light and portable to take around without having windows on my main SSD (Casual games).

    Windows 8.1 has a Windows 2 Go feature which does all you want, it's awesome!

    Just manually download the bootcamp software and install ... jobs a good'un.
  4. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    My method above is actually the unofficial Windows to Go method, derived from and modified to take into account between UEFI 2.0 Macs and Macs that don't support UEFI 2.0, and also using the built-in dism.exe instead of imagex.exe, to save the trouble of downloading WAIK.
  5. fav thread starter macrumors member

    Jul 3, 2013
    Thanks for the great follow guide! I will try in the weekend.


    I can access to Win8.1 Enterprise, but it's unstable and keeps loading sometime. Steam is one of the reasons why I want to run windows. I never heard of Windows 2 Go. I must check it out.
  6. UKgaryb macrumors regular

    Dec 13, 2013
    Manchester, UK
    It's great, you just need access to a 8.1 Enterprise machine, it's in Control Panel if you turn off the stupid "show in groups" or whatever it's called.
  7. bubulol macrumors 6502a

    Mar 7, 2013
    These following commands didnt worked for me because my 8.1 laptop is in 32 bits while i want to install 64 bits
    I am actually a bit struggling with this issue, i am thinking using my 7 64 bits computer to continue the end of this tuto (bcdboot requires same environment 32/64?)
  8. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    You can't use Windows 7 since it doesn't have dism.exe.

    And yes, it has to be 64-bit as well.
  9. bubulol macrumors 6502a

    Mar 7, 2013
    Arf, my only way out is bleep-bleep tuto but you warned me its tricky, isn't it?
    In his tuto, i think he uses MBR in boot partition while your requires GPT partition, right?
  10. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    Mine use both GPT (for UEFI) and MBR (for BIOS-CSM). My methods took into account between a BIOS-CSM installation (for pre-Haswell Macs) and a UEFI installation (for Haswell and later Macs).

    I updated the original steps already.
  11. bubulol macrumors 6502a

    Mar 7, 2013
    is it better to use GPT partition?
    I mean, i eventually managed to install W8 through external SSD by following bleep bleep tutorial
    Any installed Windows 8 on Mac, use UEFI?
  12. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    It's always better to use UEFI for significant performance gains, but only if your Mac supports it. Only Haswell and later Macs support UEFI. Ivy Bridge and later only support BIOS-CSM, because these Macs have logic boards that don't comply with the UEFI 2.0 specification.

    UEFI will only work with GPT and not MBR.

    BIOS-CSM will only work with MBR and not GPT.

    I installed Windows 8.1 in my external USB SSD (Transcend 960GB JetDrive) using UEFI, with the drive having GPT.
  13. bubulol, May 4, 2015
    Last edited: May 4, 2015

    bubulol macrumors 6502a

    Mar 7, 2013
    It eventually works after i have installed try out version of Windows 8.1 in 64 bits on my own computer
    Yes it seems to boot faster with UEFI than Bios CSM :cool:

    I forgot to mention, you must choose EFI BOOT instead of Windows partition at boot
    When i selected Windows, it got error such as ''no bootable device insert boot disk and press any key''
    Weird thing, when external SSD is connected, it starts automatically on Windows instead of manipulating alt key at boot start
    Really weird
  14. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN

    Well glad to know that my method works (again) :)

    I did mention in my post that EFI Boot had to be selected haha.
  15. bubulol macrumors 6502a

    Mar 7, 2013
    Its much faster, i like it :)
    And i must say Windows 8.1 is great OS, a bit surprising because of Metro UI but i would say its even better than OSX UI and ergonomic :eek:

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