Tutorial: How to convert a MBR partition to GPT without full format, using Windows 10

[GoodBytes]

So, you've got Windows 10. But you realize that your system is set to BIOS/Legacy mode because you used to have Windows 7, and you upgraded to Windows 10, or you cleaned installed, but never switched in the UEFI, BIOS/Legacy mode to UEFI mode, or it was set as default when you got your PC, and you forgot to change it before installing Windows 10. As a result of this, you miss out on the UEFI benefits that it brings to your computer experience such as faster startups, sleep, wake-up from sleep and secure boot,

 

You realize that, you sadly can't switch form BIOS/Legacy mode to UEFI mode in your BIOS, as if you do, Windows won't boot anymore. This is because UEFI only support GPT (GUID Partition Table), and BIOS only support the legacy system of GPT: MBR (Master Boot Record). So the only way, normally, was for format your main drive, delete all partitions it has, and restart from scratch, not to mention backup your stuff before starting the process, and restore it all. However, with Windows 10 Creators Update, Microsoft included a tool to do the conversion.

 

This tutorial will explain how, using Windows 10 Creators  Update, you can convert your drive from MBR to GPT, without clean installing your system, without data loss. And yes, it is easy! And takes a few seconds!

 

What you need?

1. Your system updated to Windows 10 Creators Updates or later.
2. A disk or USB flash drive with Windows 10 Creator Update or later on it. You can get the latest version of Windows 10 version setup here: https://www.microsoft.com/en-ca/software-download/windows10

 

Steps

"Enough talk! What are the steps!", you say.  Very good!

 

WARNING: The changes CANNOT be undone! The only way to get MBR, is a full format, and clean install. Windows 10 Creators Tool has a tool that goes only in 1 direction MBR to GPT, not the other way around.

 

CRITICAL: Many things can go wrong, Your HDD/SSD can fail, the tool might crap out on you, amongst other things. BACKUP your stuff on a separate drive before starting.

 

Before starting, let's make SURE you need to do something. In Windows 10 search box, type and pick: System Information. A panel will open in there look at the BIOS line. It should say either: Legacy or UEFI.

 

You can also check your main drive if it using GPT or MBR, by accessing its properties.

As we can see above, the drive is on MBR. So let's convert!

 

Ok so, your system is UEFI ready, and you checked above, and you saw that it says that "BIOS Mode" is set to BIOS/Legacy, and not UEFI, and your partition style of your drive is on MBR. Time to convert this!

 

1. Insert your Windows 10 disk or USB flash drive in your system, restart and boot from it. We need to do this outside of Windows, that is why we need to do boot from the Windows 10 installation. Again you need Creator Update version of Windows 10 in that disk or USB flash drive.
    
2. Once booted in Windows 10 setup, you'll see this screen
   
    
3. Click on Next, and you'll see this screen:
   
    
4. Click on Repair your computer. You'll see the a blue screen menu, with options to pick from.
    
5. On that blue menu, pick: Troubleshoot, and then pick Command Prompt
    
6. You will now have the command prompt in front of you. Type and hit Enter: mbr2gpt /convert
    
7. The tool will now convert your drive. Once done (only takes a few seconds), you can reset your computer. HOWEVER, You MUST go to the UEFI setup screen right after!
    
8. Inside your UEFI setup screen, disable CSM (Compatibility Support Module) if it is enabled, and set your UEFI mode from BIOS/Legacy Mode to UEFI Mode
    
9. Save and quit, and you should be able to start within Windows. Now, you can go back in your UEFI, and enable fast boot, if it isn't already, and you are set!

 

How does the tool works?
 

The tool works by simply making a new partition from your C:\ drive partition, and making it the EFI System Partition (this is needed for the UEFI to boot Windows after the conversion), and convert the entire drive from MBR to GPT.

 

 

As you can see from the above diagram. C:\ space is reduced to allow the EFI System Partition to fit. It isn't located at the beginning of the drive as a full format, but rather near the end.

 

Hopefully this helps in getting your system UEFI ready.

Let me know how it goes for you.

 

[RGProductions]

doing this was a total PITA when I was screwing with a macbook a few moths ago.

[GoodBytes]

2 minutes ago, RGProductions said:

doing this was a total PITA when I was screwing with a macbook a few moths ago.

I don't know what you did, Windows 10 Creator Update was not released several month ago. The tool didn't exists.

I am guessing you probably used some other tool, in which case, doesn't apply here.

[RGProductions]

Just now, GoodBytes said:

I don't know what you did, Windows 10 Creator Update was not released several month ago. The tool didn't exists.

You probably used some other tool

Oh not this, just general conversion between MBR and GPT.

[ARikozuM]

Well... I haven't used MBR in since 8 came out, but I'm glad someone made this guide. 

[Energycore]

Thanks, I still have a BIOS/Legacy only mobo so one day when I upgrade I will have to do this.

[Tech_Dreamer]

Thanks GB  ,This should come in handy .

[Alenkruth]

I did the same thing going via the Windows PE. This is the link?

 

https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt

 

Now I am facing random boot freezes and BSOD's.I use an XPS 15 9560. I have also changed to UEFI boot.Since there is no way back! Is doing a clean install the only way out?

 

[GoodBytes]

25 minutes ago, Alenkruth said:

 Is doing a clean install the only way out?

 

Sounds like it.