How to Convert GPT to MBR or Convert MBR to GPT without Losing Data?

Safe conversion between GPT and MBR disk, which is built-in AOMEI Partition Assistant, could let you manage basic disks more effectively. As you know that Windows only allows you initialize a blank disk to GPT or MBR. If there is need, you can achieve the goal with minimal effort.

June 26, 2017

How to Convert GPT to MBR or Convert MBR to GPT Disk?
About MBR and GPT Disk
MBR - Master Boot Record: it is a guide sector in the very front of drive. It was named in 1983 when partition the hard disk or flash disk of IBM compatible personal computer. At that time, PC DOS 2.0 was able to support hard disk. MBR describes the information of logical, including file system and organization type. Besides, MBR also contains the executable code produced when computer loads operating system in the second stage of start or the boot record connecting every partition (VBR). Such MBR is usually called boot routine.
Note: MBR cannot exist in a media which cannot be partitioned, such as soft disk.
GPT - GUID (Globally Unique Identifie) Partition Table: it is a new standard of disk partition table originates from EFI (Extensive Firmware Interface). Compared with MBR, it provides a more flexible disk partition principle.
What are the limitations of MBR disk?
MBR disks only support up to 2TB partition size and support only four primary partitions. If partition size surpasses 2TB, the start cannot be read and displayed. If more partitions are needed, you have to build a secondary structure known as extended partition, and then you can create logical partitions. MBR partitioning rules are complex and poorly specified. Therefore, MBR partition style is gradually replaced by GPT in such a large-disk generation.
What are the advantages of GPT disk?
It can make use of a very large size to break the 2TB limit of MBR disks.
GPT disks allow an almost unlimited number of partitions. Though Windows implementation restricts the number to 128, it is completely sufficient for using.
Each GPT partition has a unique identification GUID and a partition content type. And you can have more primary partitions.
There nearly isn’t any limitation to the size of partition. The sector is numbered by a 64-bit integer. A partition with such number of sectors, can it be small?
Partition on GPT disk has self-contained backup which is stored on the end of the disk while the original one is saved on the start. When one of the two is destroyed, you can restore it with the other.
Every partition on GPT disk can has a name which is different from partition label.
Why Do You Need to Convert MBR/GPT Disk?
As mentioned above, MBR disks only support up to 2TB partition size, so if you have a disk which is MBR formatted and larger than 2TB, you could only use 2TB disk size among it, but the rest of it could not be used. Converting MBR disk to GPT disk is considerable necessary to make full use of the disk space.
On the other hand, since Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, or Windows XP 32-bit version does not support GPT partitions. A GPT disk will display as GPT protective partition in these systems, thus you could not access the data until you convert it back to MBR disk. In such situation, you have nothing to do but to convert your GPT disk to MBR one. But note if you want to convert any larger than 2TB GPT disk back to MBR disk, you'd better ensure that the data does not account for space more than 2TB. Otherwise, the overloaded data will get lost. However, if you really want to convert your GPT drive, on which there are more than 2TB data, into MBR disk, you can transfer the extra data to other place before you start to convert.
Before you do
The following tutorial applies to converting data and system disk between MBR and GPT styles. However, if you want to convert system disk between MBR and GPT styles, please change boot mode between UEFI (United Extensive Firmware Interface) and Legacy after conversion is completed for GPT disk can only be booted by UEFI.
How to convert disk between GPT and MBR without affecting OS?
First, please Download AOMEI Partition Assistant.
Tips: If you're an individual user, please select AOMEI Partition Assistant Professional and if you're a business user, please select the edition of Sever, Unlimited or Technician.
Step1: Launch AOMEI Partition Assistant. Select the data disk you want to convert and right click it. And then select "Convert to GPT Disk" (or Convert to MBR Disk) in the drop-down menu.
Convert to GPT Disk
Step2: Click "OK" after confirming the operation.
Click OK
Step3: You can preview the conversion. To save the change, please click "Apply" on the toolbar.
For system boot disk conversion between MBR and GPT styles, to guarantee system bootable, you need to enter BIOS and change the boot mode after the conversion is completed.
For conversion between MBR and GPT disks on Laptop, please make sure the power supply is sufficient.
To ensure the data is consistent, do not abnormally terminate the program during the conversion process.
How to convert GPT to MBR without operating system?
When installing Windows 10/8/7, you may get an error saying that Windows cannot be installed to this disk. The selected disk has an MBR partition table or GPT partition table. In that case, you can convert disk between MBR and GPT before installing Windows. You can use a USB flash drive or CD to create an AOMEI Partition Assistant bootable media to convert to MBR/GPT without data loss.
1. Insert an USB flash drive or CD to another working computer running Windows 10/8/7, and launch AOMEI Partition Assistant.
2. Click on “Make Bootable CD Wizard” and follow the wizard to finish creating a bootable media.
3. Insert this bootable disk to the computer that you’re having problem installing Windows on, and then boot from the bootable media.
4. When the interface of AOMEI Partition Assistant is loaded, convert the hard drive to MBR or GPT.
After that, you should be able to install Windows on this disk. If data loss is not an issue, you can convert MBR to GPT with DiskPart utility. At the Windows Setup screen, press Windows key+F10 to bring out an command prompt, and then type “diskpart” to open DiskPart utility.