How to repair damaged MBR

Do you have problems accessing your computer? You may need to repair the MBR because it has been damaged. Here we tell you how to do it.

Are you having trouble starting your computer’s operating system? Does any error code appear on the screen? It is possible that everything mentioned is related to the boot sector being corrupted. In that case, the most normal thing is that you wonder  how to repair the damaged MBR  and regain access to your computer.

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Next, we explain everything you need to know about the MBR. First, we talk about what it is and why it gets damaged. Thus, we put you in context and you will discover if your problem is really related to this element. Additionally, we give you the appropriate instructions to repair the damaged MBR  and restore your OS. And what happens if nothing we tell you here works? Don’t worry, steps to  reinstall Windows  without losing your valuable data are also included at the end of this guide.

Index of contents

• What is the MBR and why has it been corrupted on my computer?
• How to repair the MBR on a computer step by step
  • Previous requirements
  • Open a system console in Windows installation
  • Commands to repair the MBR on your PC
• Here are the other solutions to fix the MBR

What is the MBR and why has it been corrupted on my computer?

The MBR is the  master boot record . That is,  a registry that contains the partition table of  the disk and a simple code that the operating system executes. Typically, it is in the first sector of the disk.

It can be damaged by different causes, which prevents the OS from loading normally. Here are some of the most common reasons:

• Storage drive error. It is one of the most common reasons why the master boot sector gets corrupted on a computer. As you can imagine, the operating system is hosted on one of the storage units of your computer. If there is a problem with the hard drive or partition that Windows is installed on, the  master boot record  will not be able to start up the computer.
• A virus doing its thing. Malicious programs have sometimes been developed with the aim of corrupting the MBR. This malware can enter through a variety of routes, but most often it arrives via dubious emails or Internet pages.
• Improper modifications in the MBR. Finally, boot sector corruption can be caused by changes implemented by the user or by a program. Remember that, even if modifications have been applied to the MBR that prevent the operating system from running, as long as you do not restart, you will not notice that something is wrong.

Do not miss it:

• MBR vs GPT: Differences between the most used standards

How to repair the MBR on a computer step by step

Now that we have put on the table previous information that we consider essential, it is time to tell you what the steps are to repair the MBR on a PC.

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Previous requirements

It is possible that, if you have come this far, it is because you no longer have your operating system. In that case, here’s what you need to regain access to your apps and files:

• Have another computer with Windows installed that works properly.
• A USB of at least 8 GB. The idea is to make it a bootable media to access the Windows installer.

Don’t know how to create a Windows 10 or Windows 11 bootable USB? Take a look at these guides:

• Install Windows 11 through your flash drive, make it bootable!
• How to create bootable USB Windows 10 step by step

Once you have the memory stick with Windows installed, you must meet an additional condition: configure the BIOS to boot from the  pendrive . It is just what we explain in the article  Configure UEFI BIOS to boot from USB . See instructions by clicking the link above.

Open a system console in Windows installation

The Windows installer allows you to open a system console window. Thus, the execution of commands is possible even when you do not have access to the installed operating system. How to do it?

This opens the system console in the Windows installation:

1. Wait for the installation wizard to launch.
2. Press the keyboard shortcut  Shift + F10.
3. As an alternative method, it is possible to click on the  Repair computerlink  and, from among the entries displayed on the screen, choose the  Advanced options section . Then click on  Command Prompt  or  Command Prompt .

In both cases, you will have a console window where command input is allowed.

Commands to repair the MBR on your PC

With the system console open, it’s time to run the proper commands to repair the MBR on your computer.

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They are the following:

• exe/fixmbr

About this command, the official documentation says the following:

This option writes a Windows compatible MBR to the system partition. Does not overwrite the existing partition table. Use this option when you need to troubleshoot a damaged MBR, or when you need to remove non-standard code from the MBR.

• exe/fixboot

The official documentation description reports on this command:

This option writes a Windows compatible MBR to the system partition. Does not overwrite the existing partition table. Use this option when you need to troubleshoot a damaged MBR, or when you need to remove non-standard code from the MBR.

• exe/rebuildbcd

Again, we quote from the Windows documentation so you know exactly what this command does:

This option scans all disks for installations compatible with Windows. Additionally, it allows you to select the facilities you want to add to the BCD store. Use this option when you need to completely rebuild the BCD store.

Note that it is mandatory that you execute the commands in the same order listed. To confirm the execution, it is enough that, after writing them in the console window,  press the Enter key . Different messages will appear on the screen.

Here are the other solutions to fix the MBR

In the article  How to fix the startup of Windows 10 we give you some alternative solutions that may allow you to recover the startup of the system.

If after carrying out these steps your computer is still unable to access the operating system, our recommendation is that you opt for the most effective route:  a complete reinstallation of the operating system . Obviously, first it is essential that you make a backup of your data. Visit the following links to learn how to do it yourself.

Reinstall Windows safely and without losing information : guides to do it

• How to create a backup of all your data
• Steps to generate a bootable Windows USB
• Windows 11 Installation Guide

And you, have you had problems with the MBR? How have you solved them? Tell us about your experience in the comments. We are looking forward to reading you!