How to Fix Boot Loader Errors in Windows

If you’ve ever encountered a black screen with a blinking cursor or an error message like “Bootmgr is missing” or “Operating system not found” when you try to start your Windows PC, you may have experienced a boot loader problem.

The boot loader is a small program that runs before Windows starts and tells your computer how to load the operating system.

Sometimes, the boot loader can get corrupted, damaged, or misconfigured due to various reasons, such as malware infection, hardware failure, power outage, or incorrect settings.

In this blog post, we’ll explain what each boot loader error means and how to fix them using some simple tools and commands.

Common Boot Loader Errors?

The Most Common Boot Loader Errors are:

Boot Configuration Data (BCD) missing or corrupted:

The BCD is a file that stores information about how Windows should boot, such as which partition contains the operating system, what options to use, and what order to follow.

If the BCD file is missing or corrupted, Windows won’t be able to find or load the operating system.

Boot file or MBR corrupted:

The boot file (also known as winload.exe) is a program that loads the Windows kernel into memory.

The MBR (Master Boot Record) is a section of code at the beginning of the hard drive that contains information about how to partition and format the drive.

If either of these components is corrupted, Windows won’t be able to start properly.

Operating system missing

This error means that Windows can’t locate the partition where the operating system files are stored.

This could happen if the partition has been deleted, formatted, resized, or damaged by malware or hardware issues.

Boot sector missing or corrupted:

The boot sector is another section of code at the beginning of each partition that tells the computer how to access and read the data on that partition.

If the boot sector is missing or corrupted, Windows won’t be able to recognize or access the partition where it’s installed.

Bootmgr missing or corrupted

Bootmgr (short for Boot Manager) is a program that runs after the BIOS phase and before the Windows phase of the boot process.

It reads the BCD file and displays a menu of available operating systems and options.

If Bootmgr is missing or corrupted, you won’t see this menu and Windows won’t be able to continue.

How to fix boot loader errors?

1. Use a Windows recovery disk or installation media to boot into the Advanced Startup options.
2. Select “Troubleshoot” and then “Advanced options”.
3. Choose “Command Prompt” and enter the following commands:
   • bootrec /fixmbr
   • bootrec /fixboot
   • bootrec /scanos
   • bootrec /rebuildbcd
4. Restart your computer and check if it boots up properly.

These commands will repair the Master Boot Record (MBR), the boot sector of your system partition, scan your hard drive for any installed operating systems, and rebuild the BCD store from scratch.

Here’s an Explanation of what each command of bootrec does:

bootrec /fixmbr

This command repairs the Master Boot Record (MBR), which is a small program that helps your computer boot up. If the MBR is damaged, your computer may not be able to start properly.

bootrec /fixboot

This command repairs the boot sector of your system partition.

The boot sector contains information about where the operating system is located on your hard drive, and if it’s damaged, your computer may not be able to boot up.

bootrec /scanos

This command scans your hard drive for any installed operating systems and adds them to the boot configuration data (BCD) store.

This is important because the BCD store contains information about the operating systems on your computer, and if it’s missing or corrupted, your computer may not be able to boot up.

bootrec /rebuildbcd

This command rebuilds the BCD store from scratch, using any operating systems found during the /scanos command.

This can be useful if the BCD store is damaged or corrupted, or if you have recently installed or removed an operating system.

Note:

Above commands should be entered one at a time, and you should wait for each command to complete before entering the next one.

After running all four commands, you should restart your computer to see if the boot loader error has been fixed.