Windows 10 will boot at startup but not from startup disk utility

Discussion in 'Windows, Linux & Others on the Mac' started by Bardsley, Jun 21, 2017.

  1. Bardsley macrumors newbie

    Joined:
    Jul 16, 2002
    Location:
    Australia
    #1
    I'm going to add to the chorus of Windows 10 external SSD posts, I'm sorry. But my position seems a bit different from most.
    I've installed Windows 10 on an external T3 ssd, connected to my 2017 iMac. If I hold down option when I power it up, I can select "EFI Boot" and load Windows 10 and it works fine.

    But, annoyingly, I can't select this in Startup Disk utility. A "Bootcamp" Windows drive shows up, but the bless tool won't let me select it. And when I go to disk utility it says there's a problem with the partition map.

    The think is, Windows runs totally fine and I can boot it holding down option. So I can ignore these issues, but I'd love to know if there's some way I can fix the partition map or make it work from Startup Disk, which I find a lot more convenient.
     
  2. SaSaSushi macrumors 68040

    SaSaSushi

    Joined:
    Aug 8, 2007
    Location:
    Takamatsu, Japan
    #2
    After upgrading to a new iMac and resizing my Windows 10 BootCamp install on a 500GB Samsung EVO SSD I was having similar problems. Using Winclone 6 I selected the BootCamp partition and then Tools > Make EFI Bootable fixed it for me.

    If you don't own WinClone you can download it and see if the free trial allows that feature.
     

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