UEFI Windows Boot Error: How to Restore the Bootloader

What a UEFI Boot Error Means

A UEFI boot error in Windows occurs when the system cannot find or load the boot files necessary to start the operating system within the Unified Extensible Firmware Interface (UEFI) environment. Typical symptoms include:

• The message "Secure Boot Verification Failed".
• Error 0xc000000e or 0xc0000225 indicating a missing winload.efi or bootmgfw.efi.
• A black screen with a cursor or an instant reboot.
• The absence of the "Windows Boot Manager" entry in the UEFI boot menu.

This error completely blocks access to the system, but data on the disk is usually preserved. The problem is specifically related to the boot sector and UEFI configuration.

Common Causes

1. Corrupted boot files — files like winload.efi, bootmgfw.efi, or the Boot Configuration Data (BCD) store are damaged or missing from the EFI System Partition (ESP).
2. Incorrect UEFI settings — Secure Boot is disabled, the boot order is changed, or Legacy/CSM mode is active instead of pure UEFI.
3. ESP partition damage — the partition is not formatted as FAT32, has incorrect flags, or is physically damaged.
4. Failure after an update — an interrupted Windows update or installation of drivers conflicting with the bootloader.
5. Switching from BIOS to UEFI without reinstalling the bootloader — if the system was installed in BIOS (Legacy) mode and UEFI was later enabled, the bootloader is incompatible.

Solutions

Method 1: Restore the Bootloader Using bootrec and bcdboot

This is the standard and most effective method, using built-in Windows utilities.

1. Prepare a Windows 10/11 bootable medium (USB or DVD). You can create one using Microsoft's Media Creation Tool.
2. Boot from the medium: insert it, turn on the computer, and enter the boot menu (usually F12, Esc, or Del). Select the device with Windows in UEFI mode (not Legacy!).
3. On the "Windows Setup" screen, click "Repair your computer" → "Troubleshoot" → "Advanced options" → "Command Prompt".
4. Identify the system partition letter. Often in the recovery environment, the C: drive may have a different letter. Run:

   diskpart
   list volume
   

   Find the partition with the NTFS file system and a size matching your system disk (usually C: during normal boot). Note its letter (e.g., D:). Exit diskpart: exit.
5. Run the recovery commands (replace C: with the correct letter if different):

   bootrec /fixboot
   

   This command writes boot code to the ESP partition.

   bootrec /scanos
   

   Scans disks for Windows installations.

   bootrec /rebuildbcd
   

   Recreates the BCD store. If the command asks whether to add the installation to the list, confirm (Y).
6. If the previous steps didn't help, run:

   bcdboot C:\Windows
   

   (replace C: with your system letter). This command copies boot files from the Windows folder to the ESP partition and creates a new BCD.
7. Restart the computer: close the command prompt, remove the medium, and select "Continue".

Method 2: Manually Recreate the BCD Store

If bootrec /rebuildbcd doesn't find the Windows installation, the ESP partition may not be mounted or the BCD is corrupted.

1. Boot from the installation media and open the command prompt as in Method 1.
2. Assign a drive letter to the ESP partition:

   diskpart
   list disk
   select disk 0   (usually the system disk is Disk 0)
   list partition
   

   Find the partition of type ESP (EFI System Partition) or a small partition (100–500 MB) with the FAT32 file system. Note its number (e.g., Partition 1).

   select partition 1
   assign letter=S
   exit
   

   Now the ESP partition is accessible as S:.
3. Delete the old BCD (if it exists):

   s:
   cd \
   attrib bcd -s -h -r
   del bcd
   

4. Create a new BCD using bcdboot:

   bcdboot C:\Windows /s S: /f uefi
   

   Where C: is the Windows system partition and S: is the ESP letter.
5. Restart the computer.

Method 3: Check and Repair the EFI System Partition

If the ESP partition is damaged or not formatted as FAT32, the bootloader cannot function.

1. In the command prompt (from the recovery environment), run diskpart.
2. Select the system disk and ESP partition as in Method 2.
3. Check the file system:

   detail partition
   

   The "Type" should be "System" or "ESP", and the "File System" should be FAT32.
4. If the partition is not FAT32, carefully format it (this will delete boot files, but you can restore them afterward with bcdboot):

   format S: /FS:FAT32
   

5. After formatting, run bcdboot C:\Windows /s S: /f uefi as in Method 2.
6. Exit diskpart and restart.

Method 4: Check UEFI/BIOS Settings

Sometimes the problem is not the bootloader but the firmware settings.

1. Enter UEFI/BIOS: when turning on the computer, press the key (F2, Del, F10, Esc — depends on the manufacturer).
2. Check the boot mode: set it to UEFI (not Legacy, not CSM). If there is a "Boot Mode" option, choose "UEFI Only".
3. Disable Secure Boot temporarily for diagnostics (in the "Security" or "Boot" section). After successful boot, you can try enabling it again.
4. Check the boot order: in the "Boot Priority" list, ensure "Windows Boot Manager" is first. If it's missing, the ESP partition may not be recognized — return to Methods 1–3.
5. Save changes (usually F10) and restart.

Prevention

• Do not disable Secure Boot unnecessarily — it protects against malware at the firmware level.
• Create restore points before major Windows updates or driver installations.
• Regularly back up important data to an external drive.
• When switching between BIOS/UEFI modes, always reinstall the Windows bootloader using bcdboot.
• Update UEFI firmware (BIOS) only when necessary and with caution.

Frequently Asked Questions

Can I restore the UEFI bootloader if Windows is installed on a dynamic disk?
Yes, but it's more complicated. Dynamic disks are not supported in the recovery environment by default. It's recommended to convert the disk to basic (requires backing up data) or use third-party utilities.

What to do if Windows boots after restoring the bootloader but then crashes again?
System files may be corrupted. After a successful boot, run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth as an administrator.

Why does the bootrec /fixboot command return "Access is denied"?
This happens if the ESP partition already contains boot code. Try deleting files in the ESP first (via diskpart) or use bcdboot directly without fixboot.