How to Convert MBR to GPT in Windows Server 2008 R2

by John, Updated on: October 26, 2021

Windows 2008 server has kept running for many years, the storage devices need to be replaced or upgraded with larger disks. The most common issue after upgrading disk is that you cannot use full disk space. For example, on a 4TB disk you can only use 2TB, the remaining space can't be created new or extended to other volume in Disk Management. In that case, you need to convert MBR disk to GPT. On MBR disk, you can create maximum 4 Primary partitions, if you want to create more, you also need to change disk from MBR to GPT. In this article, I'll show you 2 common methods to convert MBR to GPT in Windows Server 2008 (R2) without data loss.

1. Convert MBR to GPT with Server 2008 Disk Management

Windows Server 2008 native Disk Management has the ability to convert disk between MBR and GPT, but you must delete all partitions on this disk in advance, otherwise these options are grayed out. As you see in my test server, there are drive F: and H: on Disk 1.

When right click this disk, "Convert to GPT Disk" option is greyed out and disabled.

Convert greyed out

After deleting these two partitions, "Convert to GPT Disk" option is enabled.

Convert greyed out

Obviously, it is not a good idea to delete all partitions on a disk. Furthermore, you cannot convert system disk from MBR to GPT in Server 2008 Disk Management, because you can't delete system partition C with operating system. There are better methods to convert MBR to GPT in Windows 2008 server without losing data. The methods to convert system disk and non-system disk are different, follow corresponding method below.

2. 1-click method to change MBR to GPT for non-system disk

If you want to convert MBR disk to GPT without Operating System, it is very easy and fast with NIUBI Partition Editor.

Download this program and you'll see all disk partitions with structure and other information on the right.

How to convert MBR to GPT in Windows Server 2008 R2 with NIUBI:

Right click the front of MBR disk (here is Disk 1) and select Convert to GPT Disk.

Convert to GPT

Then there's a pending operation created on bottom left, click Apply to execute.

Apply converting

Watch the video how to convert disk from MBR to GPT in Windows Server 2008 R2:

Video guide

3. Convert system disk with MBR2GPT.exe in Server 2008 (r2)

It is a bit complicated while converting MBR disk to GPT with operating system in it. Besides keeping all files intact, the server must boot successfully. Any slight error leads to system damage or boot failure. There are some third party software that claim to be able to convert system disk from MBR to GPT, but it is always suggested to convert with MBR2GPT.exe, which is provided by Microsoft.

MBR2GPT works via command prompt, it is a native tool in Windows 10 and Server 2019. Windows Server 2008 (and R2) has no such tool, you need to download Windows Server 2019 ISO from Microsoft and create a bootable DVD or USB flash drive. If you run Windows 2008 as guest server in VMware/Hyper-V, you just need to select this ISO file and boot from it.

Precondition to use mbr2gpt.exe in Server 2008 (R2)

It is very easy to convert MBR to GPT in Windows Server 2008 with MBR2GPT command tool, but your disk partition configuration should meets the requirements below:

  1. There are maximum 3 Primary partitions on the system disk.
  2. One of the partitions is set as active and is the system partition.
  3. There's no Logical drive on the system disk.
  4. All partitions on the disk must be recognized by Windows, that means, there's no EXT2/EXT3 or other types of partition for Linux/Mac.

If any of these checks fails, the conversion will not proceed and an error will be returned, so don't worry about system and data safety.

Some people receive error when converting system disk - "Validating layout, disk sector size is: 512 bytes Disk layout validating failed for disk 0", "MBR2GPT: Conversion failed". This is common error because partition layout check fail. If your disk partition configuration doesn't meet the requirements, follow the methods below to make modification.

Convert error

Modify partition layout if needed

Press Windows and R together on the keyboard, type diskmgmt.msc and press Enter. Then you'll see disk with partition layout and other information in Server 2008 Disk Management. Check the disk partition layout if it needs to be changed.

Convert partition type:

Partition type

From this screenshot, drive D: is Logical partition. In this situation, you need to convert D to Primary partition with NIUBI.

Note: all partitions should be Primary.

Move partition to another disk:

Partition number

From this screenshot, there are 4 Primary partitions in Disk 0. In this situation, you need to move partition to another disk with NIUBI.

Note: there could be maximum 3 Primary partitions on a disk.

Steps to convert MBR to GPT in Windows Server 2008 R2 with mbr2gpt cmd

Step 1: Download Windows Server 2019 ISO and create bootable DVD or USB flash drive.

To VMware/Hyper-V virtual server, you just need to select this ISO file and boot from it.

Windows tool

Step 2: Restart server and boot from the bootable DVD or USB flash drive, when it ask you to "Install now", do not click it, click "Repair your computer" on bottom left. Then click Troubleshoot > Command Prompt in next windows.

mbr2gpt command

Step 3: You just need to input 2 commands to convert MBR system disk to GPT:

  1. Type cd.. and press Enter.
  2. Type mbr2gpt /convert and press Enter.

In a short time, MBR2GPT reports conversion completed successfully.

Convert successfully

Watch the video how to convert MBR disk to GPT in Windows Server 2008 (r2) with MBR2GPT command:

Video guide

In Summary

It is a bit complicated to convert system MBR disk to GPT, but MBR2GPT is the safest tool. If the disk has no Operating System, it is very easy to convert MBR to GPT in Windows Server 2008 R2 with NIUBI Partition Editor. Besides converting MBR to GPT, this tool helps you convert partition NTFS to FAT32, convert between Primary and Logical. It also helps you copy, shrink, extend, merge, move, defrag, wipe, hide partition, optimize file system and much more.

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