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Something got borked recently on my MBP and now Windows 10 is unbootable - here are the details.

MacBook Pro 2019, macOS 11.2.3, Windows 10 Pro x64 20H2.

  • I can see all files on the Bootcamp partition from within macOS.
  • The Startup Disk System Preference only shows my macOS volume as a boot option (when things were working normally, both macOS and Windows were startup options).
  • In the Startup Security Utility in the MBP Recovery partition, Firmware Password Protection is Off; Secure Boot is set to No Security; Allowed Boot Media is set to Allow booting from external or removable media.

Results of bless:

%sudo bless --info
Can't access "efi-boot-device" NVRAM variable

When I hold down the Option key at startup, the Windows partition is a boot option. When I select it to boot, I immediately get a blue screen with the message:

Recovery

Your PC/Device needs to be repaired A required device isn't connected or can't be accessed.

Error code: 0xc000000f

You'll need to use recovery tools...

  • I have a bootable flash drive with W10 on it. When I boot from it and attempt Startup Repair - Fix problems that keep Windows from loading, it returns after just a few seconds with the message, "Startup Repair couldn't repair your PC."

I go to the Command Prompt tools option, and here are some repair attempts and the results:

X:\Sources>bootrec /fixboot
Access is denied.

X:\Sources>bootrec /rebuildbcd Scanning all disks for Windows installations.

Please wait, since this may take a while...

Successfully scanned Windows installations. Total identified Windows installations: 0 The operation completed successfully.

DISKPART> list disk

Disk ### Status Size Free Dyn Gpt


Disk 0 Online 7663 MB 0 B Disk 1 No Media 0 B 0 B

DISKPART> list volume

Volume ### Ltr Label Fs Type Size Status Info


Volume 0 E DVD-ROM 0 B No Media Volume 1 C ESD-USB FAT32 Removable 7662 MB Healthy Volume 2 D Removable 0 B No Media

X:\Sources>bcdedit The boot configuration data store could not be opened. The requested system device cannot be found.

I would really prefer not to have to blow away the bootcamp partition and start over from scratch, although that is an option (albeit the final one) - thanks for any assistance.

Conrad
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  • Did you correctly put the correct Windows Support Software on the USB flash drive? I also suspect the Windows files were not copied to the flash drive from a Windows 10 ISO downloaded to macOS from the Microsoft website. I say this because your question shows the flash drive is FAT32 formatted. – David Anderson Apr 01 '21 at 17:47
  • @DavidAnderson I used the MS Media Creation Tool to create the bootable USB drive - it looks otherwise fine. Not sure why it didn't format it as NTFS. – Conrad Apr 01 '21 at 17:55
  • You should also be aware that bootrec /fixboot writes new boot sector to the system partition. Your Mac EFI boots Windows 10 and therefore does not use the boot sector. – David Anderson Apr 01 '21 at 17:59
  • Conrad: You made one or more mistakes because diskpart did not show the internal drive when you entered the command list disk. I can identify two possible mistakes. First, you may not have correctly created the Windows 10 USB installer. Second, the required driver did not load before entering the diskpart command. – David Anderson Apr 01 '21 at 19:33
  • You could create the USB installer by using Answer #1 posted here. Also, when booting from the USB installer, enter commands after following step 7 posted here. – David Anderson Apr 01 '21 at 19:33
  • I should also point out that your Mac can not boot from NTFS formatted partitions. For Windows, the partition should be either FAT32 or ExFAT formatted. Also, the files download using the MS Media Creation Tool differ from the files on the Microsoft Windows 10 ISO file downloaded using macOS from this Microsoft website. This is also the website Apple recommends for you to use. – David Anderson Apr 01 '21 at 19:48
  • @DavidAnderson The W10 Installer was indeed created correctly (I didn't create it; MS software did.) I redid it again anyway formatted as NTFS and same thing. Found the proper SSD driver and got it installed so it can see all the partitions within Windows installer and bcdedit says everything's fine. So there's something corrupted before Windows even boots - somehow the necessary drivers aren't being loaded with Windows. – Conrad Apr 02 '21 at 00:15
  • @DavidAnderson IDK what you mean by "your Mac can not boot from NTFS formatted partitions" - it is quite standard for Bootcamp partition to be NTFS-formatted. As already mentioned, this setup was working perfectly just a couple days ago until something got corrupted. – Conrad Apr 02 '21 at 00:17
  • The firmware stored on the logic board of your Mac boots Windows by reading the Microsoft provided Windows boot files from the EFI (System) partition. This partition is FAT32 formatted. The Microsoft provided Windows boot files stored the EFI (System) partition are capable are reading files stored in the NTFS formatted Windows partition. So I will again state: *The firmware stored on the logic board of your Mac can not read NTFS formatted partitions.* The firmware stored on the logic board of your Mac can read FAT32 and ExFAT formatted partitions along with various Apple specific formats. – David Anderson Apr 02 '21 at 04:25
  • The Install Windows 10 on your Mac with Boot Camp Assistant instructions provided by Apple have a link to a the Download Windows 10 Disc Image (ISO File) website provided Microsoft. The downloaded Windows 10 ISO file contains a install.wim file that exceeds the 4 GB limit imposed by the FAT32 format. This is why the Windows 10 installer USB flash drive needs to be ExFAT formatted. The Microsoft Media Creation Tool downloads a install.esd file instead, which is under the 4 GB limit. – David Anderson Apr 02 '21 at 04:40

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