My motherboard died in my main rig. I was in the process of planning my trip to Japan in September so I needed the OneNote files on my hard drive. I plugged my OS drive into an external dock on another computer. I left the computer do a Windows Update. When I came back that computer booted to my OS drive in the external dock. That's pretty amazing, since I'm so used to having to reformat and reinstall Windows on any new machine. Today I swapped out my broken motherboard with another spare. It booted my OS drive as well ^^
I thought I share this in case anyone was curious about moving an OS drive with Windows 10. I do have a retail key and its linked to my Microsoft Account if that means anything.