How to repair Master Boot Record (MBR) on Windows 10

• Repair Windows 10 startup problems using the Bootrec tool from the recovery environment.
• Use /fixMbr, /fixBoot, /ScanOS, and /RebuildBcd depending on the type of boot issue.
• Rebuild the Boot Configuration Data (BCD) store when Windows installations are missing from the boot menu.
• Advanced recovery commands can help resolve persistent “Bootmgr Is Missing” errors.

The Master Boot Record (MBR) is a small but critical section of a storage drive that contains the information required to locate and start Windows 10. If the MBR is damaged or corrupted, the computer may fail to boot, preventing access to the operating system.

MBR corruption can occur for a variety of reasons, including unexpected power loss, improper shutdowns, disk errors, malware infections, or changes to the system’s boot configuration. In some cases, you may encounter startup errors such as “Bootmgr Is Missing” or other boot-related messages that stop Windows 10 from loading.

When this happens, you can often repair the startup environment using the Windows Recovery Environment (WinRE) and a few Command Prompt commands, avoiding the need to reinstall the operating system.

In this guide, I’ll show you how to repair the Master Boot Record and rebuild Windows 10 boot components to get your computer working again.

Repair Master Boot Record on Windows 10

To fix MBR problems on a computer running Windows 10, follow these steps:

1. Create a Windows 10 USB bootable media.

2. Change the device firmware settings to start from the bootable media. 

   Quick tip: The process to change the settings for the Basic Input Output System (BIOS) or Unified Extensible Firmware Interface (UEFI) usually requires pressing one of the function keys (F1, F2, F3, F10, or F12), the “ESC” or “Delete” key. However, the process usually varies by manufacturer and device model. Check your manufacturer’s support website for more specific instructions.

3. Start the PC with the bootable media.

4. Click the Next button in the Windows 10 Setup.

5. Click the “Repair your computer” button in the lower-left corner.

   

6. Click on Troubleshoot.

7. Click on Advanced options.

8. Click the Command Prompt option.

   

9. In Command Prompt, use the “Bootrec.exe” tool to repair the Master Boot Record on Windows 10. The Bootrec.exe tool supports many options depending on your situation.

   Use the “FixMbr” option when you need to repair Master Boot Record corruption or clean the code from the MBR. This command will not overwrite the existing partition table in the hard drive:

   Bootrec /fixMbr

   Use the “FixBoot” option when the boot sector was replaced with another non-standard code, the boot sector is damaged, or when you installed an early version of the operating system alongside another more recent version:

   Bootrec /fixBoot

   Use the “ScanOS” option when the Boot Manager menu does not list all the operating systems installed on the device. This option will scan all drives to find all compatible installations, and it will display the entries that are not in the BCD store:

   Bootrec /ScanOS

   Use the “RebuildBcd” option when you don’t have another option, and you must rebuild the BCD (Boot Configuration Data) store:

   Bootrec /RebuildBcd

   

10. If troubleshooting the “Bootmgr Is Missing” error and rebuilding the BCD store do not fix the problem, use the following commands to export and erase the BCD store, then run the “RebuildBcd” command again to fix the Windows 10 process.

    While in the Command Prompt using the recovery environment, type the following commands and press Enter (on each line):

    BCDedit /export C:\BCD_Backup
    C:
    CD boot
    Attrib BCD -s -h -r
    Ren C:\boot\bcd bcd.old
    Bootrec /RebuildBcd

    Press Y to confirm adding Windows 10 to the list of bootable operating systems on the computer.

    

11. Click the “X” button to close the Command Prompt.

12. Restart the computer.

Once you complete the steps, the Master Boot Record will be repaired, and Windows 10 should load normally again.

If you aren’t sure what’s causing the problem with your computer, try all the commands in this guide to see if any of them resolve the issue and allow you to boot into Windows 10.

While the “bootrec” tool should be enough to repair the Master Boot Record, other related issues may require additional command-line tools (such as Bootsect.exe or BCDboot), which are beyond the scope of this guide.

Pureinfotech’s Take

In my experience, startup problems often look far worse than they actually are. When Windows 10 refuses to boot, many users immediately assume the installation is beyond repair and start thinking about reinstalling the operating system. However, I’ve found that boot-related issues are frequently tied to damaged startup files, a corrupted boot configuration, or changes to the boot record, all of which can often be repaired with the right recovery tools.

That’s why I still consider Bootrec one of the most valuable troubleshooting utilities available on Windows 10. A lot of people never think about it until a system fails to start, but these commands can often restore a computer in minutes and save users from the time-consuming process of reinstalling the operating system and reconfiguring their setup from scratch.

That said, I always recommend using these commands carefully and understanding what each one is designed to fix rather than running them blindly. The good news is that repairing the boot environment is usually much faster and less disruptive than performing a clean installation.