34

My “always on” home desktop today appeared to be totally unresponsive. It was clear that I had only one choice to power reset it. At first it seemed that it booted into my login screen, but again my I did power reset by mistake. From this point on I wasn’t able to boot. It shows “inaccessible boot device” blue screen.

Recovery or restore doesn’t work. From cmd prompt I see my C:\ drive and all files seem to be ok, entire chkdsk shows that everything is ok with the drive.

bootrec /FixMbr works, however bootrec /fixboot gives me “access is denied.”

bootrec /scanos and bootrec /rebuildbcd both show “Total identified windows installations: 0”

I tried to run it all from the UEFI partition by enabling it from diskpart but I still get “access denied” for fixboot, no matter what I tried. There is one suggestion for the “access denied” error: to format the UEFI partition and then manually create EFI\Microsoft\Boot\ in there and retry bootrec /fixboot but I find it outlandish to even consider it.

Any suggestions? What could be wrong?

36

I ran into the same issue, the suggestion from Darko_65 in Microsoft Answers forum is what worked for me:

"bootrec" command sometimes has problems finding proper boot device and windows installation to fix.

Use "bcdboot" command to fix boot (bcdboot requires that partitions are specified explicitly!)

bcdboot C:\windows /s S:

specifies C: as Windows partition, S: as system partition.

Use "diskpart" or "mountvol" commands to map system partition.
6
  • 8
    Thank you. You saved m̶y̶ ̶l̶i̶f̶e̶ my cloned win10 installation on a new SSD drive.
    – Toc
    May 18 '18 at 23:35
  • 9
    Saved my bacon too. Had cloned my SSD to a new bigger one then wiped. Just 'bcdboot C:\windows' fixed it for me.
    – AceJordin
    Dec 14 '18 at 18:32
  • 3
    Bacons are still being saved for those of us who clone to larger SSDs.
    – Fls'Zen
    Mar 6 '19 at 16:00
  • 3
    Worked for me. Simply running bcdboot C:\windows without the /s part sufficed.
    – xji
    Oct 9 '19 at 9:29
  • 1
    Worked for Windows 7 x64 in UEFI mode too. If you don't see letter/volume on GPT disk, run diskpart, then select partition X and and set id=EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
    – radioxoma
    Dec 3 '19 at 16:16
6

In the answer given by @aoetalks, copying the BCD files to new mount point didnt worked for me. It always ended up saying source files not found. It could be because my /EFI directory got corrupted.

Anyways, trying to boot with a Windows 8.1 USB media worked. All the commands, bootrec /fixmbr, /fixboot, /scanos, and /rebuildbcd worked fine and I'm back to my desktop in a few minutes.

It looks like the Windows 10 bootrec has some issues.

3
  • 3
    This should be the accepted answer. Worked for me too.
    – xyzman
    Jul 3 '20 at 6:50
  • 1
    Wow, thank you! This is what finally worked for me! I think it has something to do with Windows 10 repair tools assuming a UEFI setup. However my partition uses the legacy MBR BIOS. I used Rufus to create a bootable USB from the Windows 8.1 ISO (and set the partition scheme accordingly).
    – Jet Blue
    Aug 11 '20 at 8:36
  • 1
    August 2020 - confirmed this worked for me too. /fixboot failed persistently ("Access denied") on win 10 2004 install media. Worked first time using Win 8.1 install media.
    – Stilez
    Aug 15 '20 at 6:30
3

It's been much easier for me: after 2 weeks (!!) of Windows 10 not booting with UEFI not recognizing my GPT disk anymore, I simply used diskpart from an installation DVD/USB:

diskpart
list disk
sel disk 0
sel vol 1
attributes volume clear readonly
sel vol 2
attributes partition clear readonly 
sel vol 3
attributes... 

...worked for me so I could boot into Windows 10 after 2 weeks, WITHOUT reinstalling.

2
  • 2
    I've edited this answer to make the commands valid, as attributes partition... is not valid syntax and attributes volume... is the command that's likely being referred to instead, but I haven't confirmed that the answer works. Apr 16 '19 at 6:22
  • 2
    After selecting the EFI volume, and confirming it is active (starred), entering ATTRIBUTES PARTITION CLEAR READONLY gives 'Virtual Disk Service error: The object is not found.'
    – ndemarco
    Apr 20 at 1:58
0

After installing Windows 10 cumulative update 2021-06 for 20H2 (KB5003637) my laptop didn't boot but displayed "Operating system not found" error message. I tried @aoetalks's solution but got Failure when attempting to copy boot files. error message.

Apparently my EFI partition got somehow corrupted, since I was able to fix the issue by completely recreating the EFI System Partition with following steps:

  1. Boot from Windows 10 USB
  2. Select your region and then click Next > Repair Computer > Troubleshoot... > Advanced > Command Prompt
  3. Enter recovery key(s) if you have BitLocker enabled
  4. At the command prompt enter following commands (instructions found from NavyLCDR's post):
diskpart
lis vol  <- note which drive letter your Windows partition is assigned
lis dis <- note the disk number of the drive containing your EFI system partition
sel dis # <- replace # with the drive identified above
lis par <- note which partition is the EFI System partition
sel par # <- replace # with the partition number identified above
del par override
cre par EFI
for fs=FAT32 quick
assign letter=s
exit
bcdboot C:\Windows /s S: /f UEFI <- note may need to change C: to the drive letter identified above
exit
0

if you're here with "inaccessible boot device" and nothing else in this thread has helped you, then you're probably trying to boot from an enclosure or usb/nvme drive - you need to do this:

edit the registry HKLM/SYSTEM/HardwareConfig/{..guid..} and set BootDriverFlags = 0x14 (the guid is system specific and you could have multiples if you've booted different systems with the drive, if you're unsure which one you can just edit them all)

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