Friday, August 28, 2015

How to Transfer a Windows 10 Boot Camp Partition to another Mac

I recently got a new Mac, and found myself needing to move my Windows 10 Boot Camp partition from my old Mac to the new one. There's a great program called Winclone that can help backup and restore Windows Boot Camp partitions from within OS X. It is $40, but is a worthwhile investment, especially if you don't want to go through the hassle of re-installing and re-configuring Windows.

Although I was able to use Winclone to backup and restore my Windows partition on my new Mac, no matter what I did, I could not get the Windows partition to boot. When restarting my Mac and holding down Option, it would give me the option to select either OS X or Windows, but when selecting Windows, it would immediately boot into OS X, and wouldn't even attempt to start Windows. I re-imaged a few times, but nothing would work. This was perplexing, since I could see a properly formatted NTFS Windows partition from within OS X after restoring the image, and I was even able to browse the contents of the volume.

After much back-and-forth with Winclone support (which is great, by the way), a lot of research, and trial and error, I was finally able to get it to work using the following steps:
  • Make a backup image of the old Windows Boot Camp partition on the old Mac using Winclone
  • Delete any existing Windows partitions from the new Mac using the Boot Camp Assistant or Disk Utility in OS X
  • Download the Windows 10 ISO
  • Use Boot Camp Assistant to create a Windows install disk with a USB drive, and create a new partition, using the slider to adjust how much space you want the Windows partition to consume
  • With the Windows install USB drive plugged in, restart and hold down Option, then select EFI Boot to begin the Windows installation process (boot to the USB drive with the Windows install disk)
  • Go through the Windows 10 install process, clicking "Skip" when asked for the product key (we will be overwriting this partition in a later step--this is just to get the boot partition table--or GPT--setup properly)
  • After the machine boots successfully to Windows, and you are able to boot into Windows by holding down Option when rebooting, boot back into OS X
  • Assuming you've already imaged your Windows 10 partition with Winclone on the old Mac and transferred it to the new Mac (or loaded it from a shared network drive), launch Winclone, open the previously saved Windows image, and restore it to the newly created Windows 10 partition (it will wipe away the temporary install just created)
  • Use Boot Camp Assistant to create a USB disk with the correct device drivers for Windows
  • Reboot and hold down Option, then select the restored Windows partition, and it should boot into Windows (alternatively, you can boot to Windows using System Preferences -> Startup Disk)
  • Install the updated Windows device drivers using the Boot Camp drivers USB disk just created, then restart
Perhaps the partition table did not get setup properly when migrating from the old Mac to the new one in my first attempts using Winclone. I believe that going through a plain vanilla install of Windows 10 using the ISO and Boot Camp Assistant properly sets up the partition table and enables you to then restore and boot into the restored Windows image. Hooray for not having to re-install and setup Windows and configure apps and settings again!

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