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My laptop came with Windows 10 pre-installed using UEFI and Secure Boot on an SSD, the Windows drive encrypted with Bitlocker. I pulled that SSD and installed Ubuntu on a new SSD.

I bought an external SSD enclosure with a USB-C interface and installed the original Windows SSD into it. If I attach this drive to my USB-C port, turn on the power and go to the BIOS boot options menu, the laptop gives me the option of running the Windows boot manager on the (now external) SSD. When I select the Windows boot manager, Windows tries to boot but fails after a few seconds with a BSOD and en error "Inaccessible boot device". This is a pretty generic error and from my research may have many causes, but I think the issue is that the drive location has changed and something in the boot configuration needs to change in order for me to boot Windows 10 from this device in the external enclosure.

I've looked at the BCD Boot options, but I don't have much experience with Secure Boot, UEFI, etc., and I was hoping someone could point me in the right direction to get the configuration updated so I can boot Windows when I need it.

Robert Munn
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2 Answers2

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you just need to set HKLM/SYSTEM/HardwareConfig/{..guid..}/BootDriverFlags = 0x14 - these BootFlags correspond to CM_SERVICE_USB_DISK_BOOT_LOAD + CM_SERVICE_USB3_DISK_BOOT_LOAD.

gordy
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Just tried the answer above with setting HKLM/SYSTEM/HardwareConfig/{..guid..}/BootDriverFlags to 0x14 and it worked perfectly.

Note that 0x14 is a Hexadecimal value and is equal to 20 in Decimal

My install had 2 GUID values and so changed in both. Worked like a charm & Windows booted up as if nothing changed.

Troubleshooting a disappearing disk issue and need to isolate the inbuilt SATA controller. As I donot have the rep to upvote the above answer or add a comment to it, just adding this +1

user1270949
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