• Overview of MBR and GPT Disk
• Why need to convert GPT to MBR partition style?
• How to convert GPT to MBR without data loss in Windows PC?
• Summary

 

Overview of MBR and GPT Disk

Before learning how to convert GPT to MBR or switch from MBR to GPT, it is necessary to get a deeper understanding of MBR and GPT hard disks. On the whole, they are two different partition styles.

◤ MBR (Master Boot Record)

It is a guide sector at the very front of the drive. MBR describes the information on logical partitions and contains file systems and the organization type. It contains the boot routine – this is the executable code produced when the computer loads the OS in the second stage of the start-up or the boot record which connects every partition (VBR).

◤ GPT (GUID--Globally Unique Identifiers)

It's another partition table that has become the new standard of disk partition table originating from the EFI (Extensive Firmware Interface). It is gradually replacing MBR with something more modern. On a GPT disk, every partition has its own “globally unique identifier”.

Features of MBR partition table

▸MBR disks only support disks up to 2TB in size. If the hard disk surpasses 2TB, the additional space will show as unallocated space.
▸MBR disk only supports 4 primary partitions at most. To create more, you have to make one primary partition "extended drive", within which you can create many logical drives.
▸MBR partitioning rules are complex and poorly designed. On an MBR disk, the partitioning and boot data are stored in one place. If this data is overwritten or corrupted, it’s difficult to recover it.
▸MBR cannot be created on media that cannot be partitioned – such as CDs/DVDs.

Features of GPT partition table

▸GPT can take full advantage of a large hard drive over 2TB. The partition size is limited to 256TB as each partition in GPT can be up to 2^64 logical blocks in length.
▸GPT also allows for a nearly unlimited number of partitions. Generally, Windows allows up to 128 partitions on a GPT drive.
▸A Partition on a GPT disk has a self-contained backup at the end of the disk, with the original being stored at the front of the disk. When one of the two is destroyed, you can restore it with the other.

 

Why need to convert GPT to MBR partition style?

GPT disk seems to be more advanced when compared to MBR disk, you might still need to convert GPT to MBR disk sometimes. For example, if you are using a very old operating system like Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, and Windows XP 32-bit version, you have to convert the system disk from GPT to MBR because they cannot boot from GPT partitions. GPT disk will display as a "GPT protective partition" in these systems and you won’t be able to access your data unless you convert the drive back to MBR. Also, there are still some situations where you might need to convert GPT disk to MBR disk.

To convert the GPT disk with OS installed to MBR for better compatibility, most users might want to finish the conversion without losing data. Then AOMEI Partition Assistant Professional is a great tool, which can convert GPT to MBR (or MBR to GPT) without damaging inside data including the operating system. That is a bigger advantage than converting GPT to MBR via Command Prompt, which requires you to delete all partitions before conversion.

How to convert GPT to MBR without data loss on Windows PC?

With Partition Assistant, you can easily convert a disk from MBR to GPT and from GPT to MBR. In this article, we will only take conversion from GPT to MBR as an example. The process to convert MBR to GPT shares the same process.

Prerequisites for disk conversion

• Download and install AOMEI Partition Assistant on your PC.
• Please install the program on the currently running system if you would like to convert and make a bootable system drive.
• If you would like to convert a BitLocker encrypted system drive, it is recommended to first decrypt BitLocker encryption.
• If you would like to convert a system GPT to MBR, please first make sure your computer supports Legacy boot. On the contrary, if you want to convert a system MBR drive to GPT, please first make sure your computer supports UEFI boot.
• If you want to convert a disk larger than 2TB GPT disk to an MBR disk, you should be aware that any data above 2TB will be lost. If you still wish to convert your GPT drive to MBR you can transfer the extra data before the conversion to another drive via some helpful data migration software.
• In case of some improper operations or sudden interruptions that lead to data loss, it is better to make a backup before conversion.
• Moreover, if you can boot into Windows successfully, only 3 steps can make it done. If you cannot boot into Windows, you can create a bootable media via this software first, and then realize the conversion in WinPE mode.

The feature to convert a system drive between MBR and GPT is a paid feature. Please upgrade to AOMEI Partition Assistant Professional, Server, or higher versions to finish the operation. It is free to convert a data drive.

Situation 1. Convert GPT to MBR within Windows

1. Install and launch AOMEI Partition Assistant Professional Edition.  You can also select the system GPT disk you want to convert and right-click it, and then select "Convert to MBR" in the drop-down menu. (You can also click the "Convert" main tab and select the "Convert MBR/GPT" tool. )

If your disk is MBR and you want to convert it to GPT, please follow the same steps and choose "Convert to GPT".

2. A confirmation window will pop up. You need to select the drive you want to convert and click "OK" after confirming the operation.

3. In order to proceed the conversion, please click "Apply" on the toolbar. Then, you can preview the conversion under "Pending Operations". Then, you can click "Proceed" to start the conversion.

4. A window might pop to ask you to select a mode, either "Restart into Windows PE mode" or "Restart into PreOS mode" to execute the operation because it is a current system drive. Please select one mode you prefer to execute the conversion operation.

5. Please wait for the conversion to be finished successfully. Once it is converted successfully, the PC will be restarted automatically. And, the drive has been converted to MBR once you reboot the PC.

Tips: To boot into Windows successfully after conversion, you might need to enter BIOS to change UEFI to Legacy boot mode, or Legacy to UEFI.

Situation 2. Convert GPT to MBR without an operating system

When installing Windows 11, 10, 8, and 7, you may get an error message saying that Windows can’t be installed on this disk: The selected disk has an MBR partition table or GPT partition table. Thus you have to convert the disk from MBR to GPT (or vice versa) before OS installation. But how to convert the disk to MBR/GPT without OS installed on the PC? Don’t worry, AOMEI Partition Assistant Professional allows you to make a bootable USB drive to boot the computer without OS, and convert GPT to MBR in a WinPE environment.

1. Insert an empty USB flash drive or CD into another working computer running Windows 11, 10, 8, and 7 and launch AOMEI Partition Assistant.

2. Click the "Tools" main tab and select "Make Bootable Media".

3. Select USB Boot Device and click "Proceed" to finish creating a WinPE bootable USB.

4. Insert the bootable drive/disk into the computer that you’re having a problem installing Windows on, and enter BIOS to change boot order (make the bootable USB first), then boot the computer from the bootable media drive/disk.

5. Once logged in, you will enter the AOMEI Partition Assistant Professional interface. Then you can do the disk conversion as above to convert GPT to MBR without an operating system.

Once you have changed the disk's format you should be able to install Windows on this disk. If you are not worried about data loss you can follow the instructions here to convert MBR to GPT with DiskPart utility.

Conclusion

In this page, we not only introduce what’s MBR and GPT, what’s their limitation and advantage, and most importantly, we share a great GPT to MBR converter, which allows you to convert GPT to MBR, or MBR to GPT without data loss or operating system. Besides this amazing function, the AOMEI Partition Assistant Professional also provides many other features: clone MBR to GPT disk, clone GPT to MBR disk, migrate OS to SSD/HDD, align SSD partition, and more.

With this feature, you can easily convert a system drive or data drive between MBR and GPT without data loss. This helps you make full use of your disk and get better performances.

 

Notes:

• When converting between MBR or GPT on laptops you should make sure the laptop has sufficient power supply by connecting it to the power outlet.
• In order to protect your data, you must not terminate the program during the conversion process.
• If you are working with Windows Server, you can use AOMEI Partition Assistant Server or advanced Edition.

 

FAQs:

Q: After a GPT system drive is to MBR, what should I do to boot the PC from the MBR drive?

A: Once the conversion is completed successfully, you may need to boot your PC into BIOS/UEFI and change the Boot Mode from UEFI to Legacy.

Q: After converting GPT disk to MBR disk, what about the MSR partition?

A: The program will delete the MSR partition while converting GPT disk to MBR disk, because the MSR partition has no effect on a MBR disk.

Q: When converting the system disk from GPT to MBR, why is it prompted to install the Windows AIK or ADK when creating a bootable media?

A: The recovery partition (WRE partition) will fail after conversion. AOMEI Partition Assistant bootable media is based on the winre.wim file from the recovery partition, so you will be prompted to install the AIK or ADK. You can copy the "Recovery" folder in the recovery partition to the root directory of C: drive, and then try again.