I have put this hard drive into my XBOX one and formatted it and made sure that the XBOX one could recognize it. I was able to copy a game from the internal storage to the newly formatted usb hard drive.
I then took the hard drive to my win 7 PC and plugged it in. Win 7 recognizes it but in Admin Tools->Computer Mangment it comes up as unknown-not Initialized-unallocated.
Horizon does not recognize this drive under this condition but my XBOX one does.
Please let me know what needs to be done so that this drive is recognizable with Horizon.