How to Convert Legacy BIOS to UEFI in Windows 10 and 11

In earlier versions of Windows, you were forced to reinstall the entire operating system if you wanted to convert legacy BIOS or Master Boot Record (MBR) to UEFI or GUID Partition Table (GPT). However, a new and simple tool called MBR2GPT was introduced in Windows 10. It allows you to convert legacy BIOS to UEFI with just two commands.

Here is how you can convert legacy BIOS to UEFI in Windows 10. If you are a Windows 11 user, you should not do anything as UEFI mode is enabled by default on your device.

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Why convert legacy BIOS to UEFI?

You probably have some idea why you want to switch from legacy BIOS to UEFI, but just to confirm, here's what you need to know. Both BIOS and UEFI perform the same function on your PC – that is, built-in software built into the motherboard chip that allows you to control many important low-level things.

Your BIOS/UEFI lets you control things like boot order, connected hardware, fan speeds, physical lights on your computer, and system time. Modern motherboards even allow you to lower the voltage and overclock the CPU! It's a powerful thing.

UEFI is basically the new BIOS, doing the same job but better. With UEFI, you get (seemingly) faster boot times, greater drive capacities, better update methods and driver support, and a 64-bit mode (where the BIOS is only 16-bit).

In other words, switching to UEFI is a bit of an upgrade and worth doing. Note that even modern computers (including Windows 11) tend to still call the motherboard software BIOS, even if it is technically UEFI.

Things you need to know before converting legacy BIOS to UEFI

While converting legacy BIOS to UEFI in Windows 10 is easy, there are a few things you should know and do before proceeding.

  1. There will be no data loss when converting legacy BIOS to UEFI. (See the FAQ on this.) However, as a precaution, back up your system.
  2. You must be using Windows 10 v1703 or higher. If you're not sure, press WinR, type it winverand press Enter. On the second line, you should see “version 1703” or higher.
Win11 10 Uefi para versão do BIOS
  1. The disk you are trying to convert should have no more than three partitions. If you have more than three partitions on your Windows 10 installation drive, merge or delete the excess partitions. (See the FAQ on this.)
  2. If you are using BitLocker to encrypt your system, decrypt the drive and disable BitLocker protection before starting the conversion process. With BitLocker protection enabled, Windows 10 cannot convert your drive from legacy BIOS to UEFI.
  3. After the conversion, it may be necessary to change the motherboard firmware settings from Legacy BIOS to UEFI. Depending on your motherboard manufacturer, the procedure for switching from one to the other will be different. Have your motherboard manual handy to make things easier for you.

If you want to know more, we have a complete guide on the differences between UEFI and BIOS.

Do I need to convert legacy BIOS to UEFI in Windows 11?

If you are using Windows 11, it means that your device has passed the milestone in switching from legacy BIOS to UEFI. This is because migration to a UEFI Secure Boot is a mandatory Windows 11 compatibility requirement. There is simply no separate provisioning of legacy BIOS in Windows 11.

You can check this in the “Windows Security” option, where “Secure Boot” is displayed as Enabled. Microsoft recommends that you keep it this way to prevent any malicious software from loading during device startup.

Win11 10 BIOS para inicialização segura Uefi

Secure Boot settings can also be verified in the BIOS options (called UEFI Firmware Settings) accessible in Windows 11 “Advanced Boot”. Once the BIOS screen appears, navigate to the Boot Options tab. According to Microsoft , UEFI should be shown as the “first or only option”. This is especially true for Dell, HP and Lenovo laptops. However, some other manufacturers may have continued to maintain both UEFI and Legacy/CSM.

Boot Uefi Replace

How to check if you are using legacy BIOS

The following describes the procedure to switch from legacy BIOS to UEFI in Windows 10.

First, make sure you are no longer using legacy BIOS. After all, it's no use converting if you're already on UEFI.

  1. Search for “Create and format hard disk partitions” in the Start menu and press Enter to open the built-in Disk Management tool.
  2. Right-click the Windows installation disk, Disk 0, and select “Properties”.
Win11 10 Uefi para propriedades de gerenciamento de disco do BIOS
  1. In the Properties window, go to the “Volumes” tab. If you see “Master Boot Record (MBR)” next to “Partition style,” you are in the Legacy BIOS.
  2. If, on the other hand, “GUID Partition Table (GPT)” appears as in the image below, then you are already in UEFI and don't need to do anything else!
Win11 10 Uefi para Bios Guid

How to convert legacy BIOS to UEFI

After confirming that you are in legacy BIOS and having backed up the system, you can convert legacy BIOS to UEFI.

  1. Access Command Prompt in Windows Advanced Startup by pressing WinX.
  2. Go to “Shut down or sign out” and click the “Restart” button while holding the shiftkey.
Win11 10 Bios para Uefi desligar ou desconectar
  1. The above action will reboot your system to the advanced boot screen.
  2. Go to “Troubleshoot -> Advanced Options” and select the “Command Prompt” option.
win10-bios-to-uefi-select-command-prompt

5. Validate the disk you are trying to convert. Type the command below and press Enter.

mbr2gpt /validate

If you see the message “Validation completed successfully”, proceed to the next step. If you see any errors, your disk or system may not meet the conversion requirements.

Win11 10 BIOS para comando de validação da Uefi

If you have trouble validating at this point, enter the following command. It is highly recommended that you use this add-on code so you don't lose data.

mbr2gpt /validate /allowFullOS
Win11 10 BIOS para Uefi validar o comando com Fullos

6. After validating the disk, run the command below:

mbr2gpt /convert

As soon as you run it, Windows 10 will start the conversion process, i.e. it will add all necessary UEFI boot files and GPT components and then update the boot configuration data.

Win11 10 BIOS para Uefi Converter Comando Básico
  1. Restart the system, open the motherboard firmware settings screen and switch from Legacy BIOS to UEFI. The procedure for switching from legacy BIOS to UEFI depends on the motherboard manufacturer. Consult the manual for exact steps.
  2. After booting into Windows 10, you can check whether or not it has been converted. As before, open the disk properties window in the Disk Management tool and go to the “Volumes” tab. Here, you should see “GUID Partition Table (GPT)” next to “Partition Style”.

How to Fix MBR2GPT Error “Disk Layout Validation Failed”

When changing your hard drive from MBR to GPT, you may sometimes get the error message: “MBR2GPT Disk layout validation failed for Disk #”, with the # number referring to your boot disk.

There are two reasons for this error: more than three partitions and no space available on C drive, the boot disk.

Falha na validação do disco Win11 10 Mbr2gpt
  1. To resolve “Disk Layout Validation Failed” error, go to “Create and format hard disk partitions” in the search menu and make sure there are more than three partitions on the boot disk, Disk 0.
  2. You need to “merge and delete” some of these extra partition volumes to reduce the number of partitions to three or less. Create a backup of all important data on the extra partitions.
Win11 10 Uefi para Bios Excluir partição de volume
  1. The second reason for the error is Disk 0 drive does not have enough space for an MBR to GPT conversion. To resolve this, you need to reduce your volume to somewhere between 200MB to 2GB.

Note : If your device is already in a GPT layout, these options are grayed out.

Win11 10 Uefi para reduzir o volume do BIOS

Common questions

1. How do I switch from BIOS to UEFI in Windows without losing data?

You can easily convert legacy BIOS to UEFI without losing hard disk data. To do this, apply the /allowFullOSextension to the MBR2GPT conversion command. Even if the system is formatted, you won't lose your precious data for conversion.

Note : It never hurts to keep a backup of your most important files and folders on another computer/hard drive/USB drive or in the cloud.

Win11 10 Uefi para conversão de BIOS Fullos

2. How do I resolve the “0x514; MBR2GPT failed to enable backup/restore privileges” error in Windows 10?

Some users have experienced an “administrator not found on system” error when performing MBR to GPT conversion from a command prompt even though they were logged into the computer as an administrator. To deal with this issue make sure you are running elevated Command Prompt which is Administrator mode. It can be easily accessed from the Start menu.

Win11 10 Uefi para usuário administrador do prompt de comando elevado da BIOS

3. Can I switch back to UEFI legacy BIOS?

If you had your Windows 10/11 OS installed in UEFI mode, it is possible to revert to legacy BIOS (although we highly recommend not doing so). You must launch an “advanced boot” on your Windows device and enter the UEFI Firmware settings to disable UEFI safe mode, which can be re-enabled later.

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Felipe Santos
Felipe Santos is a Cloud and Security Architect, with experience in Windows Server, Cluster, Storages, Backups Veeam and Office 365 environments.
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