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What is GPT Partition or GUID in Windows 10/8/7

What is GUID Partition Table or GPT? In this post, we will see what a GPT partition is and how they compare to MBR disks and also how to format, remove, delete it or convert GPT disk to MBR disk. GUID Partition Table or GPT uses GUID and is a standard for the layout of the partition table on a physical hard disk.

What is GPT Partition

GPT Partition. Image source: Wikipedia

A GPT Partition is a standard for the layout of the partition table on a physical hard disk, using Globally Unique Identifiers. MBR is the abbreviation of Master Boot Record, and MBR disks are the ones that contain different sectors containing boot data. The first sector, that is, towards the beginning of the disk contains information about the disk and its partitions for the OS to use. However, MBR disks have its limitations, and many newer models of a computer are moving towards GPT disks.

Limitations of MBR Disk

An MBR formatted disk can have only four primary partitions and can manage data only up to 2TB. With data storage needs increasing, the GPT (GUID Partition Table) disks are now being sold with newer computers, that can address more than 2TB of storage. MBR disks reserve the first sector of the disk for storing information about the disk partitions and location of the operating system files.

In other words, the firmware and operating systems rely on this first sector for proper operation of the disk. If the MBR goes corrupt, you may lose general access to the data on the disk.

In the case of GPT disks, the disk information is replicated more than once, and hence such disks work, even if the first sector gets corrupted. A GPT disk can have up to 128 primary partitions.

Legacy operating systems may not support GPT disks, but almost all current operating systems, from Windows XP 64-bit onwards to Windows 8.1, support usage of GPT disks.

MBR Disk vs. GPT Disks

The main points of comparison between an MBR Disk and GPT Disk are as follows:

1. An MBR disk can contain only up to 4 primary partitions while the GPT disks can have up to 128 primary partitions

2. If you need more than four partitions, you have to create an extended partition on the MBR disks, and then you create logical partitions whereas, in the GPT disks, there is no such compulsion

3. The first sector and only the first sector of MBR disks contain information about the hard disk, while in GPT disks, the information about the hard disk and its partitions are replicated more than once, so it works even if the first sector goes corrupt

4. An MBR disk will not be able to manage disks of more than 2TB capacity while there is no such restriction with the GPT disks

5. All operating systems support MBR disks while for GPT, only Windows XP 64 bit and later Windows versions are compatible

6. For boot support, only Windows 8 supports 32-bit booting, else all preceding versions like Windows 7, Windows Vista, Windows XP 32-bit versions, cannot boot from  GPT disks.

How To Convert GPT Disk To MBR Disk

To convert a GPT disk to MBR, first of all, you will have to remove all the partitions. Before you do this, you will have to back up all the data from the disk to another disk or storage media. You can accomplish a backup using third party tools or the Windows Backup Tool.

Go to Control Panel and from Administrative Tools, select Computer Management and from the window that appears, select Disk Management. In the resulting window, that shows all disks and disk partitions in the right panel, right click and select delete for each of the partitions of the disk that you wish to convert to MBR.

Once all partitions are deleted, you will be left with one whole disk (shown as an undivided chunk in the Disk Management window). Right-click on this disk and select “Convert to MBR disk”. It will take a little while before Windows converts the disk into MBR and then formats it for making it usable.

You can now create partitions using the usual Shrink Disk command or a free third-party partition manager software such as EaseUS Partition Tool or Aomei Partition Assistant. For a detailed read, check out our post on how to convert MBR to GPT Disk in Windows 8 without data loss.

You may need to convert to MBR if you have to use a 32-bit Windows operating system on the computer. The best method would be to use two disks, one MBR, for booting purpose (the system disk) and the other GPT for storage purpose. But if you have only one disk, convert it to MBR, else it may not boot after you install, say, Windows 7 32 bit operating system to the disk. So please be careful.

This was just some basic information about GPT Disks. If you need more, you can refer the following resources:

This post will help you if your receive Selected GPT formatted disk partition is not of type PARTITION BASIC DATA GUID error.