Windows 10: How do I properly convert a MBR disk with a Windows 10 installation upgraded from 7 to a...

I was in the process of making sure my computer would be capable of upgrading to Windows 11 but I've run into a tricky issue with setting up secure boot. The motherboard in my system only supports secure boot for UEFI installations, however my system disk was originally a MBR disk installed with Windows 7 which was later upgraded via the free upgrade to Windows 10 and is still an MBR disk. To make it work with UEFI I believe I have to set up an EFI partition for Windows to boot from. I have seen the existing information about the 'mbr2gpt' tool which can do this, but ran into problems trying t

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can i convert the disk to mbr and install Windows


It 's better to let Windows do all that work for you ie. create the needed partitions whether you want to install using GPT or MBR. Here's the steps.

1. Make sure to disconnect all HD's/SSD's except the one you plan to install Windows.
2. In BIOS: disable Secure Boot. Set to UEFI if you want to install Windows in UEFI Mode otherwise set it to the legacy BIOS.
3. Boot the installation USB/DVD. Select the boot mode as shown in screen shot. It's important that you select the correct one so Windows will initialize the disk appropriately (GPT/MBR)
   
   
   
4. On the first screen, press and hold SHIFT key + F10. Command Windows pops up
5. diskpart
6. select disk 0
7. clean
8. exit
9. exit
10. Continue with the installation, click on Custom Installation and select the unallocated partition (disk 0). Do not format, click next and let Windows creates the needed partitions

 

How to convert an MBR disk into a GPT disk

Hi,

Thanks for the reply.

This is an unexpected behavior, after you convert the disk from MBR to GPT, it shouldn’t convert back automatically, however you can try to convert the disk back to GPT format if you are on Windows 10 version 1703 or later using the inbuilt utility
MBR2GPT.EXE.

• Click on Start menu (Windows logo), type
  CMD.
  
• Right click on Command prompt and select
  Run as administrator.
  
• Type MBR2GPT /validate /AllowFullOS
  
• Once the validation is successful, execute the following command and check the results.
  
• Type MBR2GPT /Convert /AllowFullOS
  
• Once the conversion is successful, you must boot the computer into BIOS and change the BIOS mode to
  UEFI.
  

Disclaimer: Modifying BIOS/ complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly.
Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.

For more information about MBR2GPT utility, please refer to the article:
Convert MBR disk into GPT using MBR2GPT.EXE

Hope it helps.

Thanks,

Peer Samie

Microsoft Community-Moderator

 

Convert only one partition on the disk from MBR to GPT

Step 2
Convert MBR to GPT without data loss