I think I've trawled the Internet for the last few days and haven't gotten any closer to my goal, to install Windows 10 on the 3rd partition of an old MacBook Pro (15-inch, Mid 2010) that I use for testing.

Problem 1: Windows ISO too big for a DVD So I first downloaded the Windows 10 from MSDN and proceeded to make an install DVD. Once downloaded, while MS says it's 4.6GB - it's clearly 4.8GB so I can't make a DVD (I don't have any DVD+R DL media). So I try the ISO to USB. Old Bootcamp Assistant (like from Yosemite) can make a bootable USB from the ISO, but it doesn't work right as BCA is running on different hardware. New Bootcamp on El Cap or Sierra won't make a bootable USB from an image period. Tried Disk Utility, hdutil and dd of which it just immediately fails when trying to write the USB. I then tried the Windows 7 ISO to USB utility from Microsoft (running inside VMWare) - and it at least got the ISO restored to the USB, however it's not bootable. The Windows Install USB drive I did make is mountable under Windows in VMWare and macOS 10.9 - 10.12. It's just not showing up as an option to boot to when holding the option key at boot.

Problem 2: Bootcamp can't seem to create a 3rd partition on my drive from the free space to install Windows Launch BCA, it does its thing by building a driver disk for 20 minutes and then goes to prep a partition. It sees 2 partitions and no free space. Even if I go back and create the partition BCA doesn't see the partition and no other partition is marked usable.

So I'm at the nexus of not quite sure how to proceed.

Has anyone added Windows as a 3rd partition on a Mac? How did you do that?

How are folks creating Mac bootable Windows install media?

Any advice much appreciated.

  • @William do you know where or how I can get an efi bootable version? MSDN doesn't show anything, and haven't had luck making one using VMWare.
    – Jim
    Commented Mar 16, 2017 at 22:19
  • VMware and virtualbox should work fine under your version of mac
    – William
    Commented Mar 16, 2017 at 23:55
  • @William virtualization isn't my issue. However I was able to use Rufus in my Windows VM to finally create a bootable Windows image. I copied the Bootcamp files onto that drive and I got further. Basically it got to the point where the Windows installer couldn't modify the boot sector to continue, and prompted me to restart the installer to continue.
    – Jim
    Commented Mar 17, 2017 at 2:08
  • you should be able to use dd to copy the iso file straight to a thumb drive without rufus, but if you have gotten it booting oh well. Do you know how to edit it using Disk Utility and gparted to get Windows booting? I have never actually done this before on a Mac so I am going of how to do this on Windows computer.
    – William
    Commented Mar 17, 2017 at 6:34
  • I don't need a special boot loader. I can hold the control key at startup to select the boot partition. I'm just not clear on the "new error" I'm having with regards to the installer having issues writing the boot partition. I'll try screen grabbing tomorrow and updating the question with current progress. I've done this whole thing with Windows many times - first time with the Mac. It's the EFI that's complicating this.
    – Jim
    Commented Mar 17, 2017 at 6:40

1 Answer 1


Here are the two issues you are facing:

Issue #1:

Disk utility shows you only two partitions, but in reality you have four; an EFI partition, and the OS X recovery partition are both hidden. Since Windows XP and Vista didn't support EFI in those days, Apple had to emulate a legacy BIOS to support Windows on that model. A legacy PC BIOS only supports MBR partitions, and MBR disks only have four entries in the partition table. Bootcamp can't create another partition that Windows would be able to see.

Issue #2:

Microsoft didn't officially support installing Windows from USB until Windows 8 came out in 2012. It was totally possible (and even easy) before that, but since Microsoft didn't support it, Apple didn't support it either. After Apple ditched the optical drives in their computers, USB was the only other way to get Windows on there, so finally Apple started supporting it. But they didn't backport the fix to earlier models so you're stuck with installing from DVD.

So here are your options:

  • You can sacrifice that 2nd partition you have and then Boot Camp will work normally.
  • You can delete the recovery partition. There are guides online on how to do this. It involves the command line. Also you have to flatten your CoreStorage volumes. Apple definitely doesn't support this but OS X works fine without it as long as you do it correctly.
  • You can find an older version of the Win10 ISO. The version you likely have is the Anniversary Update (build 1607). If you can find a 1507 or 1511 build, those will fit on a standard DVD. Once installed, you'll be upgraded to 1607 via Windows Update.

One more thing...

There are also guides out there on installing Windows in UEFI mode on a Mac. Don't do this. Your model doesn't support that and it's more trouble that it's worth. You'll run into video and audio issues (if you have dual GPUs).

Hope this helps!

  • Would you think if I sacrificed one of the Mac Partitions, then Bootcamped it, then added the third Partition back, that would work? I tried installing with DVD (ordered some DL disks and those came in and I made a proper DVD). I tried just installing with that - but got no further than I did with the GBT UEFI USB Boot. Both get to a point that say can't modify the boot sector to continue. One more thought - would the fact that my HFS+ partitions are encrypted be the problem? I just realized that was done (since all our systems are required to be encrypted).
    – Jim
    Commented Mar 18, 2017 at 6:02
  • Macs will allow as many partitions as you want, so technically speaking yes, you could add it back after Windows is installed. The problem is that you must use Disk Utility or Boot Camp to create it (they both know how to make a hybrid table properly), but both will want to take the rest of the space on the disk for it. There is no way to shrink a Windows partition after its been formatted. GParted and other tools that can shrink a Windows volume don't understand hybrid partition tables. It's really easy to eff up your partition table if you don't do it Apple's way.
    – Wes Sayeed
    Commented Mar 18, 2017 at 6:31
  • Having an encrypted drive will work fine with Windows, but that eliminates removing the recovery partition as an option. It's required for booting the system when the drive is encrypted. You probably got that error when booting because the partition table on the disk is not hybrid. Also I reiterate, do not try to boot Windows in EFI mode. It won't work.
    – Wes Sayeed
    Commented Mar 18, 2017 at 6:36
  • @WesSayeed not sure if this is true but it says here Note: After editing partitions with GParted, the hybrid partition table scheme gets out of sync. You can re-synchronize the partition tables using the gptsync command included with GParted Live, or with the rEFIt application.
    – William
    Commented Mar 19, 2017 at 22:05

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