Since I’ve had to rebuild my external SSD install of Windows 10 for use with my iMac twice since my post External SSD Gaming on an iMac, I thought I’d give an update on a more streamlined process.

But first, the two reasons I had to do the rebuilds.

  1. When Microsoft comes out with new builds of Windows 10, it appears that Windows To Go installs don’t get those updates. Since I only use the external drive for gaming, I had no problem erasing the drive and starting over with a fresh ISO with the newest build. If you save important stuff to that drive, there are hacks to make Windows not believe that it is a WTG install. But, if you bought a iMac to use Windows 10 to do work on, may God have mercy on your soul.
  2. If you have a USB flash drive with disposable information on it that you re-format regularly: name it something distinctly different from your external SSD. Otherwise, you’ll have to go through these steps again.

The revised and more streamlined process for me is:

  1. Download the newest version ISO of Windows 10 that is appropriate for your Windows 10 license.
  2. Download VirtualBox.
  3. Install Windows 10 into VirtualBox. I’d suggest not activating this install of Windows since sometimes Microsoft’s activation servers get funky if you’re using the same key twice in quick succession on two “different” computers.
  4. Download WinToUSB into the VirtualBox install of Windows 10.
  5. Unmount/eject your external SSD from your Mac, and then tell VirtualBox to use it with Windows 10 (it’s under the Devices menu).
  6. Create a Shared Folder in VirtualBox pointed at where ever you downloaded the Windows 10 ISO.
  7. Use WinToUSB to create a Windows To Go install on your SSD with that ISO. As an aside, I had my external SSD as a MBR NTFS format before I got started, and chose the Legacy option with WinToUSB. ExFAT or EFI might work, I don’t know, I didn’t try.
  8. WinToUSB took quite awhile to run. In the meantime, use the Boot Camp Setup Assistant to download the Boot Camp drivers from Apple to a USB flash drive. This will also take a surprisingly long time.
  9. Disconnect the completed Boot Camp driver USB flash drive once that’s done. This step might be important because I couldn’t get my iMac to boot into the completed Windows To Go install on the external SSD while it was connected.
  10. Boot into the new Windows To Go install on the external SSD, follow the Windows 10 setup process including installing your license key.
  11. Plug the USB flash drive back in and run the Boot Camp Assistant setup on it.
  12. Reboot.

These are more steps than on my original post, but go into a bit more detail, but is actually way less work than the first time I fumbled through this process.