failed to open efi boot mmx64.efi - not found

3 min read 01-10-2024

If you are encountering the "Failed to open EFI Boot mmx64.efi - Not Found" error while booting your system, you’re not alone. Many users have faced this issue, especially when dealing with UEFI (Unified Extensible Firmware Interface) systems. This article will dive into the causes, solutions, and preventative measures to help you troubleshoot and resolve this error effectively.

What is the EFI mmx64.efi?

The mmx64.efi file is part of the Microsoft Boot Manager for UEFI systems. It is responsible for initiating the boot process of the operating system. When your computer starts, the UEFI firmware tries to locate this file to boot the installed OS. If the file is missing or corrupted, you'll see the "Failed to open EFI Boot mmx64.efi - Not Found" message.

Common Causes of the Error

Corrupted Boot Files: If the EFI partition has become corrupted, the mmx64.efi file may be missing or unreadable.
Incorrect Boot Order: Sometimes, the system may not boot from the correct drive where the EFI file is located.
UEFI vs. Legacy Mode: If your system is set to boot in Legacy mode but the operating system is installed in UEFI mode (or vice versa), you might encounter boot errors.
Hardware Issues: Faulty hardware components, such as a failing hard drive or memory issues, can also lead to boot errors.
Software Changes: Recent updates, installations, or configurations may have inadvertently affected the boot files.

Solutions to Fix the Issue

1. Check Boot Order in BIOS/UEFI Settings

Ensure that the boot order prioritizes the correct hard drive where the operating system is installed. Follow these steps:

Restart your computer and enter the BIOS/UEFI setup (usually by pressing F2, Delete, or Esc during boot).
Navigate to the Boot menu.
Ensure that your primary disk (where the OS is installed) is at the top of the list.
Save changes and exit.

2. Repair the EFI Partition

You can repair the EFI partition using the Windows Recovery Environment. Here’s how:

Boot from a Windows installation media (USB/DVD).
Choose your language and click "Repair your computer."
Select "Troubleshoot" > "Advanced options" > "Command Prompt."

Type the following commands one at a time:

diskpart
list disk
select disk 0  # Assuming disk 0 is where your OS is installed
list volume

Locate the EFI volume (usually around 100 MB in size) and assign it a letter:
```
select volume X  # Replace X with the actual number
assign letter=Z:
exit
```

Now, navigate to the EFI folder:

cd /d Z:\EFI\Microsoft\Boot\
bcdboot C:\Windows /l en-us /s Z: /f ALL

Reboot your system and see if the error persists.

3. Disable Secure Boot

If Secure Boot is causing the issue, consider disabling it in the UEFI settings:

Restart your computer and access the BIOS/UEFI.
Find the Secure Boot option (usually under the Security or Boot tab) and set it to "Disabled."
Save changes and exit.

4. Reinstall Windows

If all else fails, you might need to perform a clean installation of Windows. Ensure that you back up your data before doing this.

5. Check Hardware

If you've tried all software-related solutions and the error continues, consider checking your hardware components:

Test your RAM for errors using Windows Memory Diagnostic.
Check the hard drive health using tools like CrystalDiskInfo.

Conclusion

The "Failed to Open EFI Boot mmx64.efi - Not Found" error can be frustrating, but with systematic troubleshooting, you can often resolve it. Whether through correcting BIOS settings, repairing the EFI partition, or checking hardware, understanding the root cause of the problem is crucial.

Remember that consistent maintenance, such as regular backups and system updates, can help prevent such issues in the future. If you have any further questions or require assistance, consider reaching out to tech forums or customer support.

Additional Resources

By understanding the nature of the "mmx64.efi" error and applying the solutions provided above, you can restore your system to normal operation and get back to work!