Repair Windows Bootloader: UEFI and MBR – 3 Ways

What Is a Bootloader and How Does It Work?

A bootloader, also known as a boot program or bootstrap loader, is a special operating system software that loads into the working memory of a computer after start-up. Windows includes bootloader components that are designed to load Windows quickly and securely. The previous Windows NT boot loader, ntldr, is replaced by three components: Windows Boot Manager (Bootmgr.exe), Windows operating system loader (Winload.exe), Windows resume loader (Winresume.exe).

Windows boot options are stored in the Boot Configuration Data (BCD) store on BIOS-based and EFI-based computers. The boot loaders reside in the root directory of each Windows partition. Once selected, the boot loaders take over the boot process and load the operating system in accordance with the selected boot parameters.

User Case: Possible Bootloader Corruption

This is a user case from the Windows 10 forum. Most people with boot issues on Windows Operating Systems (OS) will choose to reinstall the OS rather than attempt to fix the boot issue itself. In fact, there are some rescue methods that can help you solve the problem of Windows bootloader. This article focuses on providing methods to repair Windows 10 EFI bootloader. Read on to see the detailed operation.

How to Fix Windows 10 Bootloader

A computer with Windows 10 installed in native UEFI mode will fail to boot if the EFI bootloader is corrupted. The following reasons may cause startup problems related to Windows Bootloader:

✡ Install a second OS (in Dual Boot configurations)
✡ Perform incorrect actions during Windows recovery
✡ Remove some data on hidden partitions
✡ Install malicious software (virus, ransomware, etc.)

This article provides 3 methods to perform Windows 10 Bootloader repair.

Method 1. Run Startup Repair Automatically

Windows Automatic Repair is a built-in tool for users to apply and try to fix some normal errors on Windows PC. And you may also try this method to repair Windows 10 UEFI/EFI boot error:

1. Insert Windows 10 installation disk or USB to your PC. Restart PC and boot from the disk or USB. Click Repair your computer at the Install now screen.

Tip✍: if you don’t have a Windows 10 installation media, you can access the Advanced Startup environment this way: Start your PC -> Press the power button as soon as the Windows logo appears- > Keep pressing the power button to perform a hard shut. Then repeat this step two more times. -> Then choose Advanced options when the recovery screen appears.

2. Select Troubleshoot -> Advanced Options -> Startup Repair.

3. The next page displays all operating systems detected on your PC - even if you only have one installed. Click the operating system you want to repair. Then Windows will begin checking for startup problems and attempting repairs.

After the process is complete, Windows will notify you whether the repair was successful. Then you can restart your PC to see if you have fixed Windows 10 Bootloader issue.

Method 2. Repair EFI Bootloader via CMD

If Windows cannot automatically repair your PC, you can always try repairing the Master Boot Record or rebuilding the boot sector manually from the Command Prompt.

1. Insert Windows 10 installation disk or USB to your PC. Restart PC and boot from the disk or USB. Click Repair your computer at the Install now screen.
2. Select Troubleshoot -> Advanced options -> Command Prompt.

3. Type below commands and hit Enter each time:

• diskpart
• list disk
• select disk * (replace * with the hard disk that you want to repair)
• list volume

4. Verify that the EFI partition (EPS - EFI System Partition) is using the FAT32 file system. Assign a drive letter to it that is not already in use. Type below command and hit Enter each time:

• select volume * (replace * with the number of your volume that you want to assign a letter)
• assign letter=F
• exit

5. In order to repair Windows 10 EFI Bootloader, type below commands and hit Enter each time:

• cd /d :\EFI\Microsoft\Boot\ (Here replace the drive letter with the one you’re ready to repair)
• bootrec /FixBoot

6. Then you need to rebuild the BCD store by running below commands:

• ren BCD BCD.old (this command will back up the old BCD)
• bcdboot c:\Windows /l en-us /s : All (this command will recreatEthe BCD)
• exit

Note✍: If you are creating boot entries on an attached USB Flash or other external drive, add /f between the: and the ALL. Remember that the is replaced with the letter of the drive that you are booting from. (For example, C:\, D:\)

You can now restart your computer to see if the Windows 10 EFI bootloader has been resolved.

Method 3. Repair the Master Boot Record via CMD

On MBR disks, the Windows Bootloader is stored on a separate system reserved partition instead of the EFI partition. Use another guide to restore the BCD bootloader on the MBR (Master Boot Record) disk.

1. Follow Step 1.2 of the previous method to open Command Prompt in the Advanced startup environment.
2. Enter the following three commands in turn, following each by pressing the Enter key:

• bootrec /fixmbr
• bootrec /fixboot
• bootrec /rebuildbcd

3. Restart the computer with the installation media removed to check if the repair worked.

Backup System to Avoid Any System Issues in the Future

Hope you can fix Windows 10 Bootloader through the above methods. In order to prevent you from encountering similar problems in the future and then taking time to find a solution, my suggestion is that you back up the system when your computer is in good working order. In this way, no matter what boot issues or system problem you encounter, you can restore your computer to a working state through this backup.

Speaking of the most reliable backup software, AOMEI Backupper Standard is undoubtedly your best choice. It is a FREE backup and restore software for all Windows PCs (Windows 11/10/8.1/8/7/Vista/XP), including 32 bit and 64 bit. It supports you to:

✽ Create system backup, disk backup, partition backup or file backup. You can use it to back up only specific folders or entire disk on your computer.
✽ Perform incremental and differential backup. These two backup methods use less time than a full backup, and can also save the target disk space while keeping the backup up to date.Backup to multiple destinations. You can create a backup to internal/external hard drives, cloud drives, network location and NAS device.
✽ Create bootable media. If your computer has a problem and cannot start normally, you can use the bootable media created earlier to boot the computer.

If you did not create a system backup in advance when the computer crashed, you can also use the "Universal Restore" function in the Professional version to help you restore the crashed computer to a working state. You can create a system image on another functional PC using AOMEI Backupper and restore the system image to the failed computer.

Next, I will show you how to backup Windows 10 operating system via AOMEI Backupper. First, download this software on your computer.

Step 1. Launch AOMEI Backupper. Then, click System Backup under the Backup tab.

Step 2. Modify the Task Name to distinguish it from other backup tasks. The program will select the system and boot partitions by default as the source. And then choose a destination path to save the system backup.

Step 3. Click Start Backup to begin system backup in Windows 10.

Tips✍:

◉ Schedule: You can specify the intervals to backup system automatically on a regular basis, such as Daily, Weekly or Monthly. (Event triggers and USB plug in are premium features in advanced editions)

◉ Scheme: You can choose backup method from full/incremental/differential backup. You can also set up rules to delete older backups automatically so that there is enough space on your backup location. Please note "Differential Backup" and "Automatic Backup Cleanup" are only supported by paid editions.

Conclusion

Hope you can repair Windows Bootloader through the methods in this article. In the process of using the computer, we will inevitably encounter many problems, such as system problems, hardware problems and so on. It will be time-consuming and laborious to find the corresponding solution every time you encounter a problem.

Fortunately, if you use powerful software to protect your computer and data, you can avoid these laborious tasks. AOMEI Backupper can help you back up your system with just a few clicks. If you upgrade to Tech or TechPlus edition, you can also use it to deploy the same operating system to many computers.