How to Solve "GPT-Formatted Disk. Legacy Boot Not Suppor"

Help! GPT-formatted disk. Legacy boot not supported.

 

Hey everyone, I just got an HP laptop from a friend and all that it was missing was a hard drive with Windows on it. So I took my SSD with Windows  installed from my PC and plugged it into the HP. Upon boot up, it brings me to a black screen that says: GPT-formatted disk. Legacy boot not support. Press any key to reboot. Does anyone know how to go about fixing this so that I can boot into my SSD?

- Question from Reddit

The reason why "GPT-formatted disk. Legacy boot not support"?

Legacy BIOS and UEFI are two different boot modes. They are two programs embedded on the motherboard to boot the operating system. MBR and GPT are two different partition styles. Only when the partition style is set when the hard disk is initialized, can it be used to store data.

The boot mode and the partition style are not randomly matched. MBR needs to be booted by Bios, and GPT needs to be booted by UEFI. If the boot mode and the partition style do not match, your PC cannot start normally.

Therefore, if you receive the error message "GPT-formatted disk. Legacy boot not support" in Windows 7/8/10, it means that your system disk is GPT partitioned, but the boot mode of your PC is Legacy BIOS, the two don’t match. But don’t worry, we can convert GPT to MBR.

✍ Note: If you want to know more details about MBR and GPT partition styles, go to this page: What's the Difference Between GPT Disk and MBR Disk?

"GPT formatted disk. Legacy boot not supported" - Fix it right now!

Here are two ways to help you solve GPT formatted disk error. Please backup the data on the hard disk before use, because it will delete all partitions on the hard disk. The other method does not delete the data.

▶ Solution 1. Convert GPT to MBR via Windows PE

If your computer only has support for Legacy boot mode, you can convert GPT to MBR, and then your disk can boot successfully in Legacy boot mode. Since your computer cannot load Windows, you have to create a Windows PE bootable media to do that. 

Before start, you need to prepare a Windows installation USB.

Step 1.  Connect Windows installation USB to the computer and boot from it.  Press the "Shift + F10" keys on the keyboard at the same time to open the command prompt window.

2. Input bellow orders in sequence and press Enter.

●diskpart
● list disk
● select disk 1 (1 is the disk number of the hard drive you want to convert)
● clean (This operation will wipe all data on the selected hard drive, please backup important data before you start.)
● convert mbr
● exit

3. When it completes, you can go back to clean-install Windows.

▶ Solution 2. Convert GPT to MBR without losing data

In order to avoid losing data, you'd better look for an alternative tool. I will recommend AOMEI Partition Assistant Professional for you, which is a powerful GPT to MBR converter. It can convert GPT disks into MBR disks without deleting any data, and its operation is much simpler than creating Windows PE bootable media.

In addition to converting GPT to MBR, you can also use it to convert MBR to GPT for Windows 11 without data lose. Please download the Demo version to see how to solve "GPT formatted disk. Legacy boot not supported".

1. Instal and run AOMEI Partition Assistant Professional edition on another computer. In the main interface, click “Make Bootable Media” and follow the wizard to create a bootable USB drive.

2. Connect the bootable media you just created to your computer. Press the shortcut key prompted on the computer screen to enter the BIOS and change the boot drive.

3. It will bring the same interface as you previously saw. Then right-click on the disk and select “Convert to MBR Disk”.

4. Click “OK” to confirm. Then you can preview the outcome of the process. If no problem, click “Apply” apply this change to your hard drive.

After these steps, you should be able to boot your computer successfully without receiving the error message: "GPT formatted disk legacy boot not supported". One more thing you have to pay attention to is that If you receive this error on a Windows server, you can use AOMEI Partition Assistant Server Edition.

FAQs about GPT formatted disk Legacy boot not supported

Why does legacy boot not support GPT-formatted disks?

Legacy boot methods, which utilize the older MBR partitioning scheme, are not designed to recognize or boot from disks formatted with the GPT scheme. GPT offers several advantages over MBR, including support for larger disk sizes and more robust partitioning features. However, legacy BIOS systems lack the necessary firmware support to boot from GPT disks, leading to the "not supported" error.

Can I still use a GPT-formatted disk with a legacy BIOS system?
While legacy BIOS systems do not natively support booting from GPT-formatted disks, there are workarounds available. One option is to use a hybrid MBR/GPT setup, which allows you to create a small MBR partition alongside the GPT partition table to enable booting on legacy BIOS systems. However, this approach is complex and not recommended unless necessary.

Does GPT work with legacy boot?
No, GPT does not work with legacy boot methods. Legacy boot, also known as BIOS boot, relies on the older MBR partitioning scheme. GPT is designed primarily for use with UEFI systems, which offer more advanced features and security compared to legacy BIOS systems. Attempting to boot from a GPT-formatted disk using legacy BIOS will typically result in an error message indicating that GPT formatted disk legacy boot is not supported.