By Cherry / Last Updated September 9, 2019

Scenario

“I have a computer installed Windows 7. Recently, I got a 3TB hard drive and I installed it to my Windows. It had not show full usage in Windows File Explorer, this 3TB hard drive only shows 2TB. So I opened Disk Management to see what’s wrong with. And I saw it was shown as basic, online, and it had two partitions, one was formatted as NTFS about 2048GB, and the rest space is marked as Unallocated Space. I know it may because of this hard drive is an MBR disk, which maximum storage space can be recognized is 2TB, and storage space that exceeds 2TB will be shown as unallocated space. In Disk Management, if a disk is initialized as GPT, then, there is an option to convert the disk to MBR; on the contrary, if the disk is initialized as MBR, then, there is an option to convert the disk to GPT. Thus, I right-clicked the drive, and it showed as the following picture:

Cant Convert to GPT

It is no doubt that the hard drive is a basic MBR disk. I tried to convert this basic disk to GPT disk for the full use of the hard drive, but I only found the Convert to GPT Disk option is grayed out. Why I cannot convert basic disk to GPT disk?”

Why you cannot convert basic disk to GPT disk?

Actually, there are many other reasons would push users to convert basic MBR disk to GPT disk except to full use the hard drive more than 2TB. MBR disk has many limitations which can be make up by GPT disk. For example, MBR supports up to 4 primary partitions on the hard drive, while you can create 128 partitions on a GPT disk; if you want more than 4 primary partitions, convert MBR to GPT should be a good idea. However, why you cannot convert basic disk to GPT disk? Or why the Convert to GPT Disk option is grayed out?

The truth is the Windows Disk Management can only convert an empty disk to GPT disk. That means if you want to convert the basic disk to GPT disk, you have to delete all partitions on the basic disk.

How to convert basic disk to GPT disk?

To convert basic disk from MBR to GPT, here provides you three different ways, and you can choose anyone you like.

Method 1. Convert basic disk to GPT with Windows Disk Management

We have mentioned that Windows Disk Management can only convert an empty disk to GPT disk. Otherwise, you have to delete all partitions on the basic disk, and then convert the disk to GPT disk.

* Windows Disk Management does not support you delete system partition. If the basic disk contains system files, this method cannot work out.

* Before you do, you need to backup or move data on the basic MBR disk you want to convert into a GPT disk. Then, you can follow the guidance below to convert basic disk to GPT.

First, open Windows Disk Management, right click partition on the basic disk, select Delete Partition or Delete Volume.

Second, right-click the basic MBR disk that you want to change into GPT disk, and the click Convert to GPT Disk.

Finally, wait till the progress complete.

Method 2. Convert basic disk to GPT with command line

Using command line to convert basic disk from MBR to GPT also need you backup data first. And you can follow the steps below:

1. Click Start, type cmd in the search box, right-click the program and choose Run as Administrator. It will pop up a command prompt.

2. In the command prompt, type diskpart, pressEnter. When the diskpart command prompt shows up, you can type the following command to finish the task.

list disk (list all disks on your computer)

select disk (select the basic MBR disk you want to convert to GPT)

clean (this command will delete all partitions or volumes on the disk)

convert gpt (convert the selected disk to GPT disk)

Method 3. Convert basic disk to GPT without losing data

No matter Windows Disk Management or Diskpart, it will delete all data on the hard drive. Is there any way that can convert basic disk to GTP without losing data? Definitely, yes. You can take advantage of third party software like AOMEI Partition Assistant Professional, which provides you convert basic disk to GPT without losing data. What’s more, it also allows you to convert system disk between MBR and GPT without losing data.

* If you are converting system disk from MBR to GPT, you need to know:

  • 1>Windows 32bit doesn’t work on a GPT disk. If you insist to convert the MBR disk to GPT, you need to upgrade OS to Windows 64bit in advanced.

  • 2>If you want to convert system disk to GPT disk, your computer motherboard needs to support EFI/UEFI mode. Otherwise, the system will boot failure.

  • 3>Before you do, please backup your disk in case of data loss because of some bad things happened unexpected.

Step 1. Install and launch it AOMEI Partition Assistant. It will display you all hard drives on your computer in its main interface. Right click the basic disk you want to change to GPT disk, select Convert to GPT Disk.

Convert Data Disk To Gpt

Step 2. It will pop up a window to ask “Are you sure to convert the selected disk from MBR to GPT disk?”. Click OK.

Convert Data Disk To Gpt

Step 3. Here you will back to the main interface, and you can see the disk has already changed into GPT disk. Click Apply to submit the operations.

Apply To Mbr Data Disk

Wait till the progress finishes.

Note:

If you are converting system disk to GPT disk, when you click Apply, the proceed will require reboot. After converting, you need to get into BIOS and switch from Legacy to EFI/UEFI so that the converted GPT disk can boot successful.

UEFI BIOS

Those are the three methods for how to convert basic disk to GPT disk. If you meet the problem cannot convert basic disk to GPT or the Convert to GPT Disk greyed out, you can try AOMEI Partition Assistant Professional to solve the problem. Besides, AOMEI Partition Assistant provides Server edition for Windows Server users.