Changed MBR and Now Boot Device Not Found, What to Do?

In the process of installing Windows 11 on my HP laptop, I was asked to change MBR to GPT on my laptop. I put in mbr2gpt/convert in the command prompt, and since then, every time I start my laptop, it shows 'Boot Device not found' with a 3F0 error. What should I do?

Best Answered by

Roxanne· Answered on Jul 31, 2023

According to your description, the laptop shows "Boot Device not found" every time you start it since you convert the MBR to GPT while installing newer Windows. Most likely because you just converted the partition style from MBR to GPT but still need to change the boot mode to UEFI. Usually, the newer OS devices support UEFI, while the old Windows use Legacy BIOS. So, in this case, changing the boot mode from Legacy to UEFI is a must-done job.

Here is full detail about how to enable UEFI mode:

Step 1. Restart the computer before long-press the F2 key.

Step 2. Find the "Boot or System Configuration" unit and click "Boot."

Step 3. Go to "Boot," press "Enter," choose "UEFI/BIOS Boot Mode," and press "Enter."

Step 4. Choose UEFI mode, press "Enter," and Press F10 to enable and exit the screen.

There is another possibility that you have lost some data during the conversion process, which causes your computer can't find the boot device. To make things easier, you can use reliable third-party software - EaseUS Partition Master, which provides Partition Recovery Wizard to restore deleted or lost partitions.

Free Download 

Windows 11/10/8/7100% Secure

Download this tool and try to recover the lost data with easy steps:

Step 1. Open EaseUS Partition Master and find "Partition Recovery." Select the target disk and click "New Scan."

Step 2. After the scan operation, select the lost partition and hit "Recover."

(Double-click on the partition to preview content and click "OK" to confirm.)

Step 3. Click "Done" after the partition recovery process is finished.

Since converting disk from MBR to GPT via Windows built-in utility will delete data and partitions, you'd better use EaseUS Partition Master to complete the conversion. Find more information in the below link:

More Information: 4 Ways to Convert MBR to GPT

People Also Ask

Cannot Create Partition over 2TB, What Should I Do

This article provides a detailed guide on you cannot create partition over 2TB and gives a professional tool to help with this issue.


Jul 31, 2023

MBR2GPT Cannot Find Room for the EFI System Partition Error, How to Fix?

You may meet the 'cannot find room for the EFI system partition' error when you upgrade legacy BIOS to UEFI using the MBR2GPT utility.


Dec 18, 2023

I Converted My HDD from MBR to GPT Using CMD Now Windows Won't Boot

A user posted the question - I converted my HDD from MBR to GPT using CMD now Windows won't boot. To help him solve this problem, this post will introduce how to do it.


Jul 31, 2023

Can I Convert Windows 7 Boot Disk from MBR to GPT?

Looking for a solution to convert Windows 7 boot disk from MBR to GPT? This article will provide solid ways to help you convert MBR to GPT and clone the new GPT to SSD.


Jul 31, 2023

Diskpart Is showing One Partition as Two Different Ones, How Can I Do?

Are you experiencing this situation: diskpart shows one partition as two different ones when you want to convert MBR to GPT? This article will discuss how to fix the problem and convert MBR to GPT by offering a complete guide.


Jul 31, 2023

Insufficient Disk Space on Mail Server, How to Free Up

If you can't use more than 2TB of space on Windows Server, it may be due to partitioning style. This article will provide the best ways to help you expand the space on your Mail Server and solve the insufficient disk space.


Jul 31, 2023