By Bryce / Last Updated September 11, 2019

The Difference between GPT and MBR Disk

GPT disk applies globally unique identifier partition table layout, sourced from EFI, which offers more flexible disk partition mechanism. As for MBR disk, it employs master boot record layout. Due to difference of partition style, GPT and MBR present great differences in performance. MBR disk only supports four primary partitions and GPT almost unlimited number. The partition size of MBR disk is up to 2TB and GPT nearly has no limitation. What’s more, there is self-contained backup on GPT disk; if the original one is damaged, it can be resorted with the backup.

Why need to convert GPT to MBR?

As all the above mentioned that GPT disk owns so many advantages, why do you need to change the partition style of disk to MBR? Because GPT partition is not supported by Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit and Windows XP 32-bit version. In these systems, a GPT disk can not be accessed as it displays as GPT protective partition. Thus, you have to convert it to MBR disk if you want to use it in these systems above mentioned.

Convert to MBR Grayed out with Disk Management

At this time, what occurs to you firstly is to convert to MBR with Disk Management—a built-in partition tool for windows. When you run the Disk Management and right click the GPT disk, the option of “convert to MBR Disk” may be grayed out.

Convert to MBR Grayed out

You have to delete all partitions on disk 1 if you want to convert GPT disk to MRB disk via Disk Management. Therefore, you have to back up all the data and restore them after finishing conversion. It is obviously that the whole process is troublesome and bothering. Also, you can solve this problem with Diskpart utility through prompt. But you still need to suffer the trouble of backuping data and restoring them. Whether there is a better way to solve convert to MBR grayed out problem?

Solve Convert to MBR Grayed out Problem with AOMEI Partition Assistant

AOMEI Partition Assistant is reliable and safety software that helps you to convert GPT disk to MBR disk without deleting partitions. Here are the detailed steps. Firstly, download AOMEI Partition Assistant Standard and install it.

Before converting GPT to MRB, you should know:

  • As the partition size of MBR disk is up to 2TB,if you need to convert any larger than 2TB GPT to MBR disk, ensure that the used space on the GPT disk is no more than 2TB. Otherwise, the extra data will become loss.If you truly want to convert the GPT disk with over 2TB data, you can transfer the extra data or delete unimportant information before the conversion.

  • If the conversion from GPT to MBR is running on Laptop, ensure that the power supply is sufficient. Backup your important data in order to avoid other accidents, although AOMEI can convert GPT to MBR without data loss.

Step1. Run AOMEI Partition Assistant Standard and right click the disk that you want to convert to MBR (take disk 2 as an example).Then select “Convert to MBR Disk” in the drop-down menu.

Convert Data Disk To Mbr

Step2. Click "OK”.

Ok To Mbr Data Disk

Step3. You can preview the conversion. To save the change, please click "Apply" on the toolbar.

Apply To Mbr Data Disk

PS.: If your need to convert GPT disk that running Windows to MBR, you can upgrade AOMEI Partition Assistant to Professional version. Then you need to enter BIOS interface and change the boot mode after converting system disk from GPT to MBR.


It is obviously that AOMEI Partition Assistant, the great free tool is the best way to help you resolve the problem “convert to MBR grayed out” problem without data loss. It not only can convert GPT to MBR safety and effectively, but also can convert MRB to GPT. What’s more, it offers many other functions about disk partition such as resize partition and split partition so on.