Migrating Windows 10 1909 to External Drive

I’ve been trying unsuccessfully to migrate a Windows 10 Bootcamp installation from my 2019 iMac (iMac19,1) to an external drive (Samsung SSD in an OWC USB-C enclosure).

I can’t find a source for Windows build 1809, so I tried with a fresh install of the latest (1909 I believe). Installation on the iMac went smoothly, but once installed, I couldn’t get Sysprep to complete successfully. The log gives errors about preinstalled apps/services like xboxonesmartglass not being installed for all users. (paraphrasing)

I used Winclone to migrate this installation (without Sysprep) to the external SSD. Holding Option while booting shows me the external drive as “EFI”. Selecting it takes me to the Windows logo, but then I get either “Your PC ran into a problem and has to restart” or a blank blue screen. I can’t seem to access Safe Mode by holding shift.

Is this a driver problem? Should I try manually preparing Win10 for Sysprep? Should I try to find build 1809 (from questionable sources)?

Forgot to mention: after cloning Windows to the external drive, that drive doesn’t show up in Startup Disk

It does sound driver related. Did you enable external booting in Startup System Utility?


External Boot isn’t an option in Startup Security Utility, I believe this is because this iMac doesn’t have a T2 security chip.

I did precisely the same thing about a month ago, offloading my BootCamp from my macBook to a Samsung SSD. I wish I could remember the specific details, but I did have more than a bit of trouble. From memory, I used sysprep in Win10, which pretty much eliminated all of the parameters in Win10. At least 2 or 3 times, I went to the winClone log to discover a problem that I was able to correct. Finally, I did get it to complete under WinClone. Once the WinClone image was complete, I restored it to a exFat partition on my Samsung SSD, while leaving the 2d exFat partition untouched. The 2d partition allows me to transfer files from macOS to Win10. Winclone reformatted the 1st exFat partition under NTFS and loaded the image. It works nicely now with my macBook. It loads like any BootCamp partition. It even works without any modification with my partner’s iMac ‒ no need for extra drivers. Convinces me that Win10 works better with Mac machines than with any other - go figger!

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Do you remember what Windows build you installed? Would it have been from here: https://www.microsoft.com/en-ca/software-download/windows10?

Using the latest build (1909) I wasn’t able to get sysprep to complete successfully.

No I do not remember. It’s an installation from a long time ago, originally Win7 that was migrated (for free, by the way) to Win10.

Do you know where I could find that information in the system? If so, I can look it up.

John Waller

I did have trouble with sysprep. I had to search the Web a bit to find answers. Once it completed OK, I did WinClone and had some issues. These were noted in the WinClone log and I was able to resolve them.

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