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?
5 Answers
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.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.
3It'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.
2After 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:
- Boot from Windows 10 USB
- Select your region and then click Next > Repair Computer > Troubleshoot... > Advanced > Command Prompt
- Enter recovery key(s) if you have BitLocker enabled
- 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
exitif 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)
