Convert MBR Disk to GPT Without Dataloss?

Converting a disk from MBR (Master Boot Record) to GPT (GUID Partition Table) is essential for users who want to utilize modern features like UEFI boot mode or handle disks larger than 2.2 TB. This guide will walk you through different methods of converting MBR to GPT with and without data loss. This guide also covers converting MBR to GPT during Windows installation.

Convert MBR to GPT with Data Loss (During Windows Installation)

This method involves converting the disk to GPT during the Windows installation process and can also be followed if you need to convert the disk to GPT with Data loss.

1. Restart Installation: Restart your computer and boot from the installation media if you are stuck at conversion during Windows Installation. Otherwise please skip this step to step 2!
   Once you are on the Windows installation screen, press the Shift + F10 keys simultaneously. This will open the Command Prompt window.

2. Access the Command Prompt: In the Command Prompt window, type diskpart and press the Enter key.

diskpart

3. Open DiskPart Utility: To view all available disks on your computer, type list disk , and press the Enter key. This command displays a list of all disks along with their statuses, sizes, and partition types.

list disk

4. List Available Disks: Determine which disk you want to convert from MBR to GPT. Identify the disk by its number from the list provided.
   For example, if the disk to be converted is Disk 0, type select disk 0 and press Enter.

select disk <disk number>

Warning: The following step will erase all data on the selected disk. Ensure you have backed up all necessary data before proceeding.

5. Clean the Disk
   To wipe the disk clean, type clean and press Enter. This command will remove all partitions or volumes on the disk, effectively erasing all data.

clean

6. Convert Disk to GPT: After cleaning the disk, type convert gpt and press Enter key. This command will change the partition style of the disk from MBR to GPT.

convert gpt

7. Return to the Windows Installation Process: Once the conversion is complete, close the Command Prompt by typing exit or clicking the close button.

exit

You will return to the Windows setup screen. Proceed with the installation process by creating new partitions on the newly converted GPT disk as needed.

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Convert MBR to GPT Without Data Loss (Using MBR2GPT Tool)

This method uses the mbr2gpt tool and allows you to convert a disk from MBR to GPT without losing any data. This tool is built into Windows 10 and Windows 11 and can be run from a Windows installation environment or a running Windows system.

[Important] Although this method is designed to avoid data loss, it is always recommended to back up your important data before proceeding.

1. Open Command Prompt as Administrator: Open the Start menu, type cmd, right-click on Command Prompt, and select Run as administrator.

2. Validate the Disk for Conversion: Run the following command to validate the disk and ensure it meets the requirements for conversion:

mbr2gpt /validate /disk:0 /allowFullOS

Replace 0 with the disk number you want to convert.

3. Convert the Disk: If the validation is successful, run the conversion command:

mbr2gpt /convert /disk:0 /allowFullOS

This command will convert the disk from MBR to GPT without deleting your data.

4. Change BIOS Settings: After conversion, restart your computer and enter the BIOS/UEFI settings. Change the boot mode from Legacy (or CSM) to UEFI.

5. Reboot and Confirm: Save the changes in BIOS/UEFI, and reboot your computer. Your system should now boot using the GPT partition style.

Both methods have their use cases depending on whether you want to keep your data or start fresh. For new installations or when data loss is not a concern, converting with data loss during Windows installation is simpler. For converting an existing system without losing data, the mbr2gpt tool is the best option.