MBR2GPT is a command-line tool provided by Microsoft, which is used to convert a disk from Master Boot Record (MBR) to GUID Partition Table (GPT) without modifying or deleting data on the disk. This tool is particularly useful when you want to switch from BIOS to UEFI boot mode, as UEFI requires a GPT disk.

Understanding MBR and GPT:

• MBR (Master Boot Record): An older partitioning scheme that supports up to four primary partitions and a maximum disk size of 2TB.
• GPT (GUID Partition Table): A modern partitioning scheme that supports larger disk sizes and more partitions, essential for UEFI boot mode.

Prerequisites:

1. Ensure your system supports UEFI.
2. Backup your data to prevent any accidental loss.
3. The disk should not have more than three partitions.
4. The disk should not have any extended/logical partitions.

Steps to Convert MBR to GPT Using MBR2GPT:

1. Open Command Prompt in Windows Recovery Environment:

   • Boot your system into Windows Recovery Environment (WinRE). You can do this by holding the Shift key while clicking Restart.
   • Navigate to Troubleshoot > Advanced options > Command Prompt.

2. Validate the Disk:

   Before converting, validate the disk to ensure it meets all requirements.

   mbr2gpt /validate /disk:<disk number> /allowFullOS

   Replace <disk number> with the number of the disk you want to convert. You can find this number by running diskpart and then list disk.

3. Convert the Disk:

   If the validation is successful, proceed with the conversion.

   mbr2gpt /convert /disk:<disk number> /allowFullOS

   This command will convert the disk from MBR to GPT.

4. Change Firmware Settings:

   After conversion, you need to change your firmware settings from BIOS to UEFI.

   • Restart your computer and enter the BIOS/UEFI setup (usually by pressing a key like F2, F10, DEL, or ESC during boot).
   • Change the boot mode from Legacy BIOS to UEFI.

5. Boot into Windows:

   Save the changes and restart your computer. It should now boot using UEFI mode from the GPT disk.

Examples:

• Validating a Disk:

  If your disk number is 0, the command will look like this:

  mbr2gpt /validate /disk:0 /allowFullOS

• Converting a Disk:

  To convert the same disk, use:

  mbr2gpt /convert /disk:0 /allowFullOS

Troubleshooting:

• If you encounter errors during validation or conversion, ensure that no partitions are in use and that the disk meets all prerequisites.
• Check for any disk errors using chkdsk and resolve them before proceeding.