How to Repair the Windows Bootloader With bootrec Commands

How the Windows boot chain breaks

On a BIOS/MBR machine, boot goes through the master boot record, the boot sector and a file called BOOTMGR, which reads the BCD store — the database listing Windows installations and their boot parameters. On the far more common UEFI/GPT machine the chain is shorter: the firmware loads bootmgfw.efi from the 100 MB EFI System Partition, and that file reads the same BCD. A failed update, a power cut during boot, a disk clone that dropped the ESP, or installing Linux alongside Windows are the classic ways for any link in this chain to break.

The symptoms are unambiguous: BOOTMGR is missing, a 0xc0000e “required device is inaccessible” screen, an empty boot menu, or INACCESSIBLE_BOOT_DEVICE. Which command you need depends on the firmware type — and getting into WinRE to run anything at all is step zero.

• bootrec /fixmbr — rewrites the MBR (BIOS/MBR systems only; useless on UEFI/GPT)
• bootrec /fixboot — writes a new boot sector to the system partition
• bootrec /scanos — scans all disks for Windows installations absent from the BCD
• bootrec /rebuildbcd — rebuilds the BCD store and offers to add the installations it found
• bcdboot C:\Windows /s S: /f UEFI — the actual repair on UEFI systems: fresh boot files to the EFI partition

Getting into WinRE and running the bootrec ladder

If Windows fails to start, interrupting the boot three times in a row — powering off as soon as the spinner appears — makes Windows 11 open the Recovery Environment by itself; choose See advanced repair options → Troubleshoot → Advanced options → Command Prompt. With installation media instead: boot the USB, click Next on the language page, then Repair your computer → Troubleshoot → Advanced options → Command Prompt. From that prompt, the classic ladder for a BIOS/MBR machine is bootrec /fixmbr, bootrec /fixboot, bootrec /scanos, then bootrec /rebuildbcd, answering Y when it offers to add the installation it found.

Two cautions before you press Enter. First, /fixmbr overwrites whatever bootloader owns the MBR — on a dual-boot machine with GRUB that means Linux stops booting until you reinstall GRUB from its own media. Second, if /rebuildbcd answers “Total identified Windows installations: 0”, do not start deleting BCD files on a UEFI machine; on BIOS the documented route is attrib -h -r -s C:\boot\bcd, then deleting the file and re-running /rebuildbcd — but on UEFI the correct move is the bcdboot route below.

The UEFI route: bcdboot to the EFI partition

On a UEFI machine the repair consists of rewriting the boot files on the EFI System Partition. In the WinRE Command Prompt, run diskpart, then list disk, select disk 0, list partition, select the small 100–260 MB FAT32 partition (the ESP), assign letter=S and exit. Now bcdboot C:\Windows /s S: /f UEFI copies a fresh set of boot files and rebuilds the BCD; adjust C: if Windows sits on another letter in WinRE — use diskpart or dir C: to verify which letter holds the Windows folder before running anything.

The known wart: on some builds bootrec /fixboot answers “Access denied” even from WinRE; the accepted workaround is to skip it and use bcdboot, which writes the same files by a different route and bypasses the failing code path. Whichever route worked, exit WinRE, pull the USB stick and boot normally — and once Windows is up, run sfc /scannow and chkdsk to clean up whatever the failed boot left behind.

Questions and Answers

Read next

All articles · FAQ