By Emily / Last Updated October 12, 2019

When need to convert a GPT disk to an MBR disk?

Although most customers choose GPT as the disk style due to its more advantages over MBR before the first use, sometimes they might need to convert a GPT disk into an MBR disk. The most important reasons should be the limitations of OS support on a GPT disk (not all operating systems can be installed on GPT disk):

1. The early operating systems including Windows 2000, Windows MS-DOS/NT, Windows 95/98, Windows Vista 32-bit and XP 32-bit are not unable to read, write and boot from a GPT disk.

2. All versions of Windows Vista/XP/7/8/10 and Windows Server 2003/2008/2012/2016 can use GPT disk to store data. But only 64-bit editions on UEFI-based systems can be used as system disks.

If you try to install Windows 7 32-bit on a GPT disk, you will fail with an error message "Windows cannot be installed to this disk. The selected disk is of the GPT partition style". Therefore, you need to convert to MBR disk

Option “Convert to MBR disk” not available in Disk Management

When it comes to converting the disk to MBR from GPT, you might immediately turn to Disk Management - a built-in disk/partition management tool for Windows. But when you run it and right-click the GPT disk, you might find the option “Convert to MBR Disk” not available or clickable, which prevents you from converting it to MBR disk.

Convert To Mbr Disk Not Available

Why “Convert to MBR Disk” not clickable in Windows?

The main cause might be there are partitions on the chosen disk. In Disk Management, you can only convert an empty disk (without any partitions) to MBR or GPT disk. So, when the chosen disk has partitions on, you will find the option “Convert to MBR Disk” or “Convert to GPT Disk” greyed out.

How to solve “Convert to MBR Disk” not available easily?

Now that we have found out what triggers this problem, it will be easy to get the solution -delete all partitions from the disk before you begin the converting process from GPT. Specific steps are below:

Warning: you can copy partition to another hard drive to make a backup because deleting partition will remove all data from it,

Step 1. Right-click on each partition on the disk you want to convert to MBR, and select “Delete Volume”.

Delete Volume For Convert Mbr

Step 2. In the pop-out small window, click “Yes” to confirm your operation. And wait for the process to be finished.

Step 3. After the entire disk becomes an unallocated space, you right-click the GPT disk and select “Convert to MBR Disk”. Now it is clickable.

Convert To Mbr Clickable

Step 4. Follow the wizard to complete the conversion.

Besides, you can also use Diskpart utility to convert disk to MBR. It also requires you to delete all partitions on the GPT disk first of all, so back up anything required.

First, click "Search" box on the desktop and input "cmd" in it, right click the program and select “Run as Administrator” to open the prompt window.

Then type the following commands in turn and press Enter after each one. (Here we take converting disk 1 to MBR as an example)

Diskpart->list disk->select disk 1->clean->convert mbr

Convert MBR Diskpart

Best way to resolve it without deleting partitions/losing data

As you can see, to solve “Convert to MBR Disk” not available issue in Disk Management or Diskpart, deleting all partitions on the chosen disk is a must procedure. If you store lots of important data within the disk, you have to back up data, then delete partitions and finally restore them after conversion, quite time-consuming and troublesome, right?

So, is there another way to solve this problem without deleting volumes? Yes, AOMEI Partition Assistant Standard can satisfy you best. It supports converting GPT to MBR and vice versa no matter whether there are partitions on the target disk. Below we will show you how to convert a GPT disk to MBR without deleting all partitions in Windows 10.

Step 1. Download the freeware. Install and launch it, right click the GPT disk and choose "Convert to MBR Disk". You can see there is a NTFS partition on this disk.

Convert To MBR

Step 2. When the message “Are you sure to convert the selected disk from GPT to MBR disk” pops out, click "OK" to continue.

MBR OK

Step 3. Hit on "Apply" to commit the GPT to MBR conversion.

MBR Apply

If you want to convert GPT to MBR without loading operating system, you can first create a bootable media via AOMEI Partition Assistant, and boot PC from it to make the conversion in Window PE mode.

Bonus tips:

  • Because the MBR partition table can only support 2TB disk at most, it is not advised to convert an over 2TB GPT disk to MBR. If you force convert it to MBR, you might meet hard drive showing wrong capacity issue then.

  • Although this method won’t require you to delete partitions first, we still suggest that you should back up disk to avoid data loss resulted from some uncontrollable factors.

  • If you want to convert boot disk between MBR and GPT styles, you should upgrade AOMEI Partition Assistant to Pro version, which also enables you to finish the conversion without deleting system volumes.

Further reading

Additionally, we found that some users are searching for answers to the questions: “how do I know if my disk MBR or GPT”, and “how do I repair MBR disk”. So, today we will also clear your doubts on them.

▶Part 1. How to tell the disk is MBR or GPT?

To check the partition table style of one disk, you can locate the disk in the Disk Management window. Right-click it and select “Properties”.

Then access to the “Volumes” tab. In the “Partition style”, you will see either “Master Boot Record (MBR)” or “GUID Partition Table (GPT)”.

▶Part 2. How to repair MBR disk?

Repairing MBR disk, in most cases, means repairing MBR (Master Boot Record) on the hard disk, which holds vital information about the partitions your hard drive. If it is damaged, you may be unable to access the hard disk. So learning how to repair MBR on disk is of importance.

Luckily, AOMEI Partition Assistant Standard comes with a function named “Rebuild MBR”, which can rebuild the corrupted MBR in 3 steps.

Step 1. In its main interface, right-click the disk with corrupted MBR and select “Rebuild MBR”.

Rebuild Data Disk Mbr

Step 2. Choose a proper MBR type for your current OS and click “OK”.

Choose Mbr Type

Step 3. Click “Apply” and “Proceed” to commit the pending operation.

Conclusion

AOMEI Partition Assistant is an effective tool to solve convert to MBR disk not available issue without losing data or removing partitions. Besides, it also has some other great functions such as NTFS to FAT32 Converter, which enables you to convert NTFS to FAT32 and vice versa without causing data loss, cloning MBR disk, migrating OS from MBR to MBR disk.

For Windows Server users, AOMEI Partition Assistant Server is a great choice.