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Boot Camp / Dual Boot on an iMac 27" Mid 2011

Dual Booting on an iMac 27" Mid 2011

UPDATE: See comment section below this post.

This guide is so complicated because the iMac's 27" Mid 2011 SuperDrive doesn't recognise the windows install disc. It's useless.

IMPORTANT: Unplug all external and physical hard drives (where possible) that you won't be installing to to avoid accidentally erasing them. Also make note of which drives and partitions remain (e.g. System and Storage hard drives), and be super careful to not erase the wrong one.

RECOVERY: If you nuke your machine, restore your time machine backup. Instructions here.

Windows 8.1

UPDATE: Because of the issues listed later on, I've decided that Windows 8 via Boot Camp is futile. Trying Windows 7 SP1 instead.

  1. Remove your firmware key by restarting, holding alt, choosing recovery, then in "utilities" choose "firmware assistant" or something
  2. Download the "bootcamp drivers" from here, as of 15 September 2014, for the iMac Mid 2011, these are the latest
  3. Create a Time Machine Backup
  4. Create a mac bootable windows usb drive by either (windows install dvd will not boot on EFI systems):
  5. Using "Bootcamp Assistant" on your Macbook Air
  6. Or by modifying your iMac's Bootcamp Assistant using sudo vi /Applications/Utilities/Bootcamp Assistant/Contents/Info.plist and adding it to the HAR listing, the USB listing and the EFI listing. Remove "Pre" from the USB and EFI listings if it is there
  7. Create the partition by either:
  8. Using "Bootcamp Assistant". Then to avoid the error Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks. use gdisk to delete the "Hybrid MBR" setup that "Bootcamp Assistant" created, gdisk instructions here
  9. Using "Disk Utility" to resize the OSX partition and leave the free space free
  10. Boot into the installation media by restarting, hold alt key, and selecting "EFI"
  11. Install windows on the partition
  12. To avoid the error Windows could not prepare the computer to boot into the next phase of installation. To install Windows, restart the installation. later when installing, delete the first partition called EFI on the partition screen 1. UPDATE: This is likely the cause of Issue 1
  13. On the partition screen delete partitions 4 and above and use the unallocated space for the windows partition


  • Once all installed. Windows can boot to OSX, but OSX and Windows cannot boot to Windows (error No bootable device -- insert boot disc and press any key). Instead you must use the "alt" on startup technique. Doing a Windows Repair & Diagnose Startup Problems does not fix the issue.
  1. Audio doesn't work. Updating to latest Realtek drivers doesn't fix it. May be related to Hardware updates with Windows Update. Could be AMD drivers instead.

  2. Only 2.5GB of Memory is available out of my 16GB. I have four 4GB sticks inside the iMac and running Windows 8.1 x64. Can not figure out how to fix this.

Windows 7 SP1

  • Doesn't work when using the Macbook Air's Bootcamp Assistant to create the USB Drive. Errors with: No bootable device -- insert boot disc and press any key error
  • Testing via unbootin now.


  • Don't use the 14.04 AMD64 MAC image, it doesn't boot! Ironic and ANNOYING! Same annoying result for unetbootin on GUID, MBR, and via dd, and dcfldd methods.

  • Instead use the 14.04.1 AMD64 image, it does boot. Tested with unetbootin on GUID and MBR, both work.


  • Install rEFInd, it's the next version of rEFIt. It will show all the available boot devices, even ones that can't be booted (No bootable device -- insert boot disc and press any key error). Often the "Fallback" boot device is the one you want. You always want the EFI boot device.

  • There is a "EFI Boot" that is a Windows 8 Recovery still persistant, even though the entire HDD has been wiped and reinstalled via the OSX USB Install.

    • This guide which uses diskpart's clean all works for getting rid of that recovery sector.
      • If you then install windows 8.1 ontop of the new cleaned partition it still has the audio and memory issues as before. Seems like it could be an EFI thing.
  • This may be a better install guide than the usual ones.

  • This may work for booting from the external superdrive.

    • Without Bootcamp (just the alt on startup) just get a black screen with blinking cursor
    • Have not yet tried with bootcamp.
  • This tool or this tool may also work.

    • Rufus EFI only on ? only boots, but doesn't load. Just hangs on boot.
    • Refus EFI&BIOS on MBR doesn't boot, shows windows logo then does the No bootable device -- insert boot disc and press any key error
    • Microsoft's tool doesn't detect the USB drive (tried on VMWare Virtual Machine and on a Windows Physical Machine)
  • This guide could work for using VMWare to get the initial setup going.

  • This guide could work for getting Windows 7 to boot on EFI.

    • Didn't work. Had the same hard freeze issue as Rufus EFI only had.

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coax commented Sep 28, 2014

Thanks for this. I had Windows 7 SP1 x64 installed (27" iMac 12,2) 3 years now until today when decided to do clean install of Windows 8.1 x64. After 12 hours of trying every possible way to make them pass the partition screen, I just gave up and went back to 7.


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tkeeler33 commented Jan 28, 2015

Hey, I just wanted to comment that I was able to successfully install Windows 8.1 on my Mid 2011 27" iMac. I spent a bunch of time trying to get the USB install method to work, and had all the same problems here (without success). The only way I was able to get it installed (without any issues) is to burn the Windows 8.1 x64 ISO to a DVD-R, and use the boot camp assistant to build a bootable USB stick (8GB). It rebooted and installed Windows 8.1 from DVD seamlessly. I only had to format the bootcamp partition to NTFS during Windows setup. I know you mentioned your SuperDrive didn't recognize your Windows DVD, you may want to try another disc or perhaps there's a problem with your drive.

I hope this helps, I wasted a lot of time trying to hack the USB install method and it clearly doesn't work (which is why apple hides this option for this iMac).


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tylercasson commented Feb 14, 2015

Wow looks like DVD-R was the key. I had only tried with a DVD-RW and the SuperDrive could never read it. It would just spin up and down. Just tried with a new disk and I'm up and running flawlessly. Thanks for that, @tkeeler33


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Raghidozes commented Jun 19, 2016

I bought the Imac 2011 and the Windows 7 was installed.
After five years, I had to remove the windows 7 from boot camp
I did that, and update to the mac os to El capitan - fresh installed
After that I tried all the ways to install Windows 7 from boot camp without result...
"insert boot disc and press any key"
I need help ..... I wasted my time
I've tried burned copy and my Orginal DVD still the same (insert boot disc and press any key)
from internal optical and Apple USB SuperDrive, I've tried them both
I'm loosing my mind


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balupton commented Sep 9, 2016

Been a while since I've touched this, so my memory may be rusty, however I suspect I got it working by not modifying anything, and burning the Windows 10 ISO to a DVD via the official tool on a windows computer, then putting into the mac's superdrive (and ejecting and reinserting until the mac's built-in superdrive actually recognises it) - seems the superdrive works erratically, and for older macs that don't provide a USB bootcamp option, do not try to use USB as it will cause more headaches - just get a working DVD disc. Pretty much exactly that @tkeeler33 and @tylercasson say!


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hidrogen83 commented Feb 21, 2017

I installed Windows 8 64bit, via usb dongle (efi boot) on BootCamp partition. I notice the no audio problem (there is a device called "High Definition Audio" on system device that cant run properly and show code 10).
I've already tried to install latest Realtek High definition audio codec, but still having this problem.
Anybody had the same problem and resolve it?
I've an iMac 2011 mid.

Thanx in advice


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GambitGR commented Jul 10, 2017

After Spending 3 weeks Reading and trying all different methods. The only windows I managed to install without any problems was Windows 7 x32 edition. The Imac mid 2011 DVD Seems to work on x32 version but not on x64. Its not the discs as I've I tried about 20 different discs from TAIYO YUDEN To TDK Verbatim etc. Its seem that it can read all my x32 Windows 7 but has difficulties on the x64 edition. Try it yourself too and let me know. Gluck. BTW I also installed Windows 10 but Im getting BSOD when bootcamp is trying to Install the intel graphics and no sound seems to work.

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