When a PC shows "BOOTMGR is missing," "Boot Configuration Data file is missing," or simply cycles through a black screen and reboots without ever reaching the Windows logo, the Boot Configuration Data (BCD) or the Windows Boot Manager itself has usually become corrupted, rather than the operating system files. This is one of the more fixable boot failures because the repair tools are built into Windows itself — you just need to reach them. This guide walks through diagnosis and repair using the Windows Recovery Environment.

Safety warning: Before running any repair commands, if the PC contains data you haven't backed up, consider connecting the drive to another PC (via a USB SATA/NVMe enclosure) to copy off important files first, if the drive itself is accessible and the fault is genuinely boot-related rather than a failing drive. Boot repair commands are generally safe and don't touch personal files, but any time you're troubleshooting boot failures it's worth confirming your data is protected in case the underlying problem turns out to be more serious.

Understanding the Boot Chain

When a Windows PC starts, UEFI firmware locates the boot manager (bootmgfw.efi on UEFI systems, or BOOTMGR on older legacy BIOS/MBR systems), which reads the Boot Configuration Data store to find and load Windows itself. Corruption anywhere in this chain — a damaged BCD store, a missing boot manager file, or an incorrect UEFI boot entry — prevents Windows from loading even though the operating system files on disk may be completely intact. This is why boot repair often fixes the problem in minutes without any data loss: it's rebuilding the map to Windows, not Windows itself.

Common Symptoms of Boot Manager Corruption

  • "BOOTMGR is missing. Press Ctrl+Alt+Del to restart."
  • "The boot configuration data for your PC is missing or contains errors."
  • A black screen with just a blinking cursor and no further progress.
  • The PC boots straight to UEFI/BIOS setup or a "No bootable device found" message.
  • Automatic Repair loops: Windows attempts to repair itself, fails, and restarts into the same attempt repeatedly.

Step 1: Reach the Windows Recovery Environment

  1. If Windows attempts to boot and fails, interrupting it three times in a row (holding the power button to force a shutdown during the loading screen, three times consecutively) usually triggers Automatic Repair and drops you into the Windows Recovery Environment (WinRE) automatically.
  2. If that doesn't work, boot from Windows installation media — a USB drive created on another PC using the Microsoft Media Creation Tool. Set the affected PC to boot from USB in its boot menu (usually F12, F11, F10, or Esc during startup, varying by manufacturer), then on the setup screen click Repair your computer rather than Install now.
  3. From the recovery screen, select Troubleshoot > Advanced options > Command Prompt.

Step 2: Identify the Partition Layout

Before running repair commands, it helps to confirm you're working with the correct drive letters, since WinRE often assigns different letters than Windows normally uses.

  1. In the Command Prompt window, type diskpart and press Enter.
  2. Type list disk to see connected drives, then select disk 0 (adjust the number if you have multiple drives).
  3. Type list partition to see the partition layout — look for a small EFI System Partition (typically 100–300MB, formatted FAT32) and the larger main Windows partition.
  4. Type exit to leave diskpart.

Step 3: Run the Standard Boot Repair Sequence

These four bootrec commands, run in order, resolve the large majority of BCD and boot manager corruption cases.

  1. Type bootrec /fixmbr and press Enter — this writes a fresh master boot record without overwriting the existing partition table, safe for both legacy and UEFI systems.
  2. Type bootrec /fixboot and press Enter — this writes a new boot sector. If this returns "Access is denied," see the troubleshooting note below.
  3. Type bootrec /scanos and press Enter — this scans all disks for Windows installations compatible with the current boot method, confirming Windows itself is still present and detectable.
  4. Type bootrec /rebuildbcd and press Enter — this rebuilds the Boot Configuration Data store. When prompted "Add installation to boot list?", type Y and press Enter.
  5. Type exit and restart the PC to test.

Pro tip: If bootrec /fixboot returns "Access is denied," this is commonly caused by the EFI System Partition not being assigned a drive letter in the recovery environment. Use diskpart, select the EFI partition (identified in Step 2), run assign letter=Z, exit diskpart, then retry the bootrec /fixboot command.

Step 4: Rebuild the BCD Manually with bcdboot (If bootrec Fails)

If the standard sequence doesn't resolve the issue, bcdboot rebuilds the boot files directly from the Windows installation, which is more thorough than bootrec /rebuildbcd.

  1. From the same Command Prompt, confirm your Windows partition's drive letter (commonly C: in WinRE, but verify with dir C:\Windows to check the folder exists — if not, try D: or another letter).
  2. Type bcdboot C:\Windows /s Z: /f UEFI (replacing C: with your confirmed Windows drive letter and Z: with your EFI partition letter from Step 3) and press Enter. For legacy BIOS systems, replace /f UEFI with /f BIOS, or use /f ALL if you're unsure which firmware mode the PC uses.
  3. Restart and remove the installation media to test a normal boot.

Step 5: Check the UEFI Boot Order

Sometimes the boot files are entirely intact, but the UEFI firmware's boot order has been changed or the Windows Boot Manager entry has been removed — common after a firmware update, a new drive being added, or a dual-boot setup being altered.

  1. Restart the PC and enter UEFI/BIOS setup (commonly Del, F2, or F10 during startup).
  2. Look for a Boot Order or Boot Priority section and confirm Windows Boot Manager is listed and set as the first boot device, rather than a network boot option, USB, or a different drive.
  3. Save changes and exit (usually F10) to restart.

When These Steps Don't Resolve It

If the boot repair sequence completes without errors but the PC still fails to boot, the underlying cause may not be boot manager corruption at all but a failing drive, corrupted system files beyond the boot chain, or a Windows Update that damaged core files. At that point:

  • Run chkdsk C: /f /r from the same recovery Command Prompt to check for and repair file system errors on the drive itself.
  • Try System Restore from Troubleshoot > Advanced options > System Restore if a restore point exists from before the fault began.
  • As a last resort that preserves personal files, use Troubleshoot > Reset this PC > Keep my files to reinstall Windows while retaining your data — see our guide on resetting Windows 11 without losing your files for the full walkthrough.

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