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10 Tech How-To

How to Clone MBR Disk to GPT in Windows 10

Guide 10-32424 · Updated · Step by step

This guide walks you through converting a Master Boot Record (MBR) disk to a GUID Partition Table (GPT) disk in Windows 10, either by cloning the entire disk or by converting an existing system disk without data loss. You’ll learn the prerequisites, the step-by-step process using built-in tools and free third-party software, common pitfalls, and troubleshooting tips.

What You’ll Need

  • A Windows 10 PC with the source disk (MBR) and a destination disk (if cloning).
  • An external USB drive or a second internal disk with enough capacity to hold all data from the source disk.
  • If converting a system disk in place, a Windows 10 installation USB or recovery drive (optional but recommended).
  • Administrator access to the PC.
  • Backup of important data (always recommended before disk operations).

Step-by-Step

Method 1: Clone MBR Disk to GPT Using Disk Management and DiskPart (For Data Disks)

  1. Back up your data. Before any disk operation, copy important files to an external drive or cloud storage.
  2. Open Disk Management. Press Win + X and select Disk Management.
  3. Identify the source disk. Note the disk number (e.g., Disk 0, Disk 1) of the MBR disk you want to convert.
  4. Initialize the destination disk as GPT. If you’re cloning to a new drive, right-click the destination disk and choose Convert to GPT Disk (if available). If the option is greyed out, you may need to delete all volumes on that disk first (this erases data, so ensure it’s empty).
  5. Clone the partitions. Windows doesn’t have a built-in clone tool. Use a third-party tool like Rufus (for bootable USB) or Macrium Reflect Free to clone the disk. For this guide, we’ll use Macrium Reflect:
    1. Download and install Macrium Reflect Free.
    2. Launch it and select Create an image of the disk or Clone this disk.
    3. Choose the source MBR disk and the destination GPT disk.
    4. Follow the wizard; ensure the destination is set to GPT partition style.
    5. Start the clone and wait for completion.
  6. Verify the clone. After cloning, open Disk Management and confirm the destination disk shows as GPT and has the same partitions.

Method 2: Convert MBR to GPT In-Place Using MBR2GPT (For System Disks)

  1. Check system requirements. Your motherboard must support UEFI boot. Most PCs from 2012 onward do. Also, the disk must have at least 3 partitions (typically System Reserved, C:, and possibly a recovery partition).
  2. Back up your data. This is critical; although the tool is designed to be non-destructive, backups are essential.
  3. Open Command Prompt as Administrator. Press Win + X and select Command Prompt (Admin) or Windows PowerShell (Admin).
  4. Run the validation command. Type mbr2gpt /validate /disk:0 (replace 0 with your disk number) and press Enter. If validation succeeds, you’ll see “Validation completed successfully.”
  5. Convert the disk. Type mbr2gpt /convert /disk:0 and press Enter. The tool will convert the partition table to GPT and update the firmware boot entries.
  6. Reboot. After conversion, restart your PC. Enter BIOS/UEFI settings (usually by pressing F2, Del, or Esc during boot) and set boot mode to UEFI (disable Legacy/CSM).
  7. Test boot. Save changes and exit. Windows should boot normally.

Common Mistakes

  • Not backing up data. Even with non-destructive tools, a power failure or software glitch can corrupt data.
  • Using the wrong disk number. Double-check that you’re converting the correct disk, especially if you have multiple drives.
  • Forgetting to switch to UEFI boot mode. After conversion, the BIOS must be set to UEFI, not Legacy/CSM, or Windows won’t boot.
  • Ignoring the validation step. Running mbr2gpt without validation can fail midway, leaving the disk in an inconsistent state.
  • Cloning to a disk with existing data. The destination disk must be empty or have all volumes deleted; otherwise, the clone may fail or overwrite data.

Tips

  • Use the MBR2GPT tool for system disks. It’s the only built-in method that preserves data and is designed for this exact purpose.
  • Check if your PC supports UEFI. In BIOS, look for a “UEFI” or “Secure Boot” option. If absent, your motherboard is too old.
  • Keep the destination disk larger or equal to the source. If the source has more data than the destination capacity, the clone will fail.
  • For cloning, use a tool that supports GPT. Some older cloning software only creates MBR on the target. Macrium Reflect and AOMEI Backupper are reliable free options.
  • After conversion, enable Secure Boot (optional). GPT works with Secure Boot, which adds a layer of protection.

Troubleshooting

  • Validation fails with “Cannot find OS partition.” This usually means the system partition is missing or the disk has more than 3 partitions. Ensure the disk has a System Reserved partition (100 MB) and the C: drive. If not, you may need to create one using a Windows installation USB.
  • After conversion, PC won’t boot. Re-enter BIOS and ensure boot mode is set to UEFI, not Legacy. If it still fails, boot from a Windows installation USB, open Command Prompt (Shift+F10), and run bootrec /rebuildbcd and bootrec /fixmbr (note: /fixmbr may not work on GPT, but /rebuildbcd is key).
  • Clone process fails with “Disk is too small.” The destination must have at least the same usable space as the source. Check the source’s total used space and compare with destination capacity.
  • Disk Management shows the destination as “Unallocated” after cloning. This can happen if the clone tool didn’t copy the partition table correctly. Re-clone with a different tool or manually create partitions and copy data.
  • “The specified disk is not convertible” error. This occurs when the disk has more than 3 primary partitions or has dynamic disks. Convert dynamic to basic first, or remove extra partitions.

Frequently Asked Questions

Can I convert MBR to GPT without losing data?

Yes, using the MBR2GPT tool for system disks is non-destructive. For data disks, you can use third-party cloning tools that preserve data, but always back up first.

Will converting to GPT improve performance?

No, GPT doesn’t directly improve read/write speeds. It allows for more than 4 primary partitions and supports disks larger than 2 TB, and it’s required for UEFI boot.

Do I need to reinstall Windows after converting?

No, the MBR2GPT tool converts in-place without reinstalling. Cloning also preserves the OS, so no reinstall is needed.

What if my motherboard doesn’t support UEFI?

Then you cannot boot from a GPT disk. You must stay with MBR or upgrade your hardware. GPT is only bootable on UEFI systems.

Can I convert back from GPT to MBR?

Yes, Windows has a similar tool called gptmbr (not built-in), but it’s not recommended. You’d need to wipe the disk or use third-party tools. There’s no built-in GPT to MBR converter that preserves data.

Is it safe to use free third-party cloning tools?

Yes, reputable free tools like Macrium Reflect Free and AOMEI Backupper are widely used and safe. Always download from official websites and scan for malware.

Related

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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