By Catherine / Last Updated June 21, 2019

About MBR and GPT

MBR (Master Boot Record) is the old style of disks and is widely used by users. For MBR disks, you can create 4 primary partitions at most and the maximum size of each disk is 2 TB. In order to create more partitions, you have to build a structure of less than 3 primary partitions + one extended partition. Extended partitions is a logical part of a hard disk, it can be used to create more logical partitions.

GPT (GUID Partition Table) is the latest disk style. It makes full use of globally unique identifiers to define the partition and it is a part of the UEFI standard. As for GPT disks, you are able to build unlimited partitions on the hard disk.

There are differences between MBR and GPT. Sometimes, in order to satisfy the various demands of the users. It is necessary to convert between MBR and GPT.

When Do You Need to Convert MBR Partition Table to GPT?

Situation1: When you install Windows 8, you may encounter an error that stated: "Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI system, Windows can only be installed to GPT disks."

However, this could happen not only Windows 8, but also Windows 7 and Windows Server 2008, 2008 R2.

Situation 2: you have a 4TB hard drive which was been initialized as MBR style with no awareness, you must convert it to GPT style to make full use of its disk space, because MBR can’t support partitions which are larger than 2 TB.

Others: MBR can only support 4 primary partitions at most, but you want to create more partitions; you need to reinstall your system or you realize your basic disk is unveiled.

Why is it Need GPT and How to Convert to GPT?

Obviously, Windows can only be installed to GPT disks because of your EFI system. So the solution is to convert MBR to GPT? Yes, it is. But how to convert is a big question.

Of course, you can use Disk Management a built-in tool. But the disadvantage is that you may have to delete all partitions if there are partitions on your disk. And you need little technical stuff to be manipulated yourself. Following is Microsoft suggested solution:

Besides, you can use Command Line to convert MBR to GPT. However, it is not data protective either and not every user is familiar with Command Line. So, if you don't want to delete all partitions and create partitions from the scratch and install the OS or using the complicated methods. Is there any simpler way to fix this problem?

Yes! I found a work around to this problem. Without deleting all partitions you can achieve this. Just use a disk converter named an AOMEI Partition Assistant Professional Edition.

AOMEI Partition Assistant Pro is designed for Windows home users. With its powerful features such as allocating free space, converting dynamic disk to basic disk, migrating OS to SSD, Making bootable CD, you can manage your partitions easily and safely. Furthermore, all of the functions can be supported by Windows 8.1, Windows 8, Windows 7, Vista, XP, 2000.

Step by Step Guide to convert MBR to GPT without losing data:

  • Download AOMEI Partition Assistant Professional Edition from its official website.

  • Install and run. We can see the MBR disk from the main interface. Right click it and select "Convert to GPT disk".

    Convert System Disk To GPT

  • Click "OK" and "Yes" in the pop-up windows.

    OK To GPT System Disk

  • Now we can see the pending operations and click "Apply" to commit the changes.

  • Apply To GPT System Disk

Then we will say good bye to "Windows cannot be installed to this disk. the selected disk has an MBR partition table. On EFI system, Windows can only be installed to GPT disks". Just four steps, we get rid of the irritating messages. So I think it is the simplest way.

With this powerful disk converter, we can optimize our partition easily. Such as convert FAT/FAT 32 to NTFS, convert primary to logical partition, migrate OS to SDD and so on. We can even make a portable Windows 8 by using the function of "Windows To Go Creator".