Trying to convert MBR to GPT in Windows 10

Question

I have been trying to follow the instructions for creating bootable WinPE media. I have downloaded the Assessment and Deployment Kit and Windows Preinstallation Environment (WinPre) to my desktop. I have updated WinPre.

I have the Windows 10 System (C:) set up in one partition, Windows Home (D:) : set up in a second partition and a 516MB Recovery partition on Disk 1.

I have formatted a USB Drive (G:) - FAT32 - 4.67 GB

I have opened the Deployment and Imaging Tools environment and the command prompt:

C:\Windows\system32> ... but can get no further.

Please help me with the correct command prompts to install WinPe on this USB so that I can convert the MBR to GPT. (or other directions as appropriate).

I operate a dual boot computer with Linux Kubuntu on one HDD (Disk 0) and Windows 10 (Disk 1) on another. Linux is GPT/UEFI. In recent months I have been losing access to Windows 10 when needing to do a restart to install a major Windows update... GRUB error. I guess I have two options: try this 'convert' approach or reinstall Windows 10 or install Windows 11 and specify GPT in the setup.

Answer 1

To create a bootable WinPE media on your USB drive and perform the MBR to GPT conversion, follow these steps:

Step 1: Prepare WinPE Files

1. Make sure you have the Windows Assessment and Deployment Kit (ADK) installed on your desktop. You mentioned that you have downloaded it, so ensure it's the latest version.
2. Locate the installed WinPE files on your computer. They are usually found in a path like: C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\Oscdimg

Step 2: Open Command Prompt

1. Click on the Start menu, search for "Command Prompt," right-click on it, and select "Run as administrator" to open an elevated command prompt.

Step 3: Navigate to the WinPE Files Directory

1. In the Command Prompt, navigate to the directory where you found the Oscdimg utility. Use the cd command to change directories. The command will look like this (update the path according to your installation location):

cd "C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\Oscdimg"

Step 4: Create WinPE ISO

1. Now, you will use the Oscdimg utility to create the WinPE ISO image. Use the following command:

oscdimg -n -m -bC:\path\to\boot\etfsboot.com C:\path\to\WinPE\ISO C:\path\to\WinPE\WinPE.iso

Explanation of the parameters:

• -n: Allows long filenames (required).
• -m: Enables ISO 9660 file format with no Microsoft Joliet extensions.
• -b: Specifies the path to the boot sector file (etfsboot.com). Replace C:\path\to\boot\etfsboot.com with the correct path to etfsboot.com on your system.
• C:\path\to\WinPE\ISO: Replace this with the path where you want to create the temporary ISO files (it will be used to create the final ISO).
• C:\path\to\WinPE\WinPE.iso: Replace this with the desired path and filename for the final WinPE ISO file.

Step 5: Copy WinPE to USB

1. After creating the WinPE ISO, you need to extract its contents to the USB drive (G:). You can use a tool like 7-Zip to do this, or you can use the built-in File Explorer in Windows 10.
2. Once you have extracted the contents of the WinPE ISO to the USB drive, you should have a bootable WinPE USB.

Step 6: Convert MBR to GPT

1. Boot your computer from the WinPE USB.
2. Once WinPE is loaded, open Command Prompt from within WinPE.
3. Use the diskpart utility to convert the MBR disk (Disk 1 in your case) to GPT. Be extremely careful while using diskpart as it can erase data if not used correctly.

Here are the steps to convert MBR to GPT using diskpart:

diskpart
list disk
select disk X  (Replace X with the number of the MBR disk)
clean
convert gpt
exit

Remember to replace X with the appropriate disk number of the MBR disk you want to convert to GPT.

1. Verify the conversion using the list disk command again. The disk should now be listed as GPT.

Answer 2

I very much appreciate your help. (https://learn.microsoft.com/en-us/users/na/?userid=432e03d6-efbc-40d3-9268-bcacdada6246)

I moved the Assessment and Deployment Kit and Windows Performance Toolkit back from the Desktop into "Windows Kits" .

I have followed your instructions to get an Administrator command prompt (i.e. C:\WINDOWS\system32>) and entered the following command as per the file path on my computer:

cd "C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\Oscdimg"

I then entered:

oscdimg -n -m -bC:\path\to\boot\etfsboot.com C:\path\to\WinPE\ISO C:\path\to\WinPE\WinPE.iso

I got this error message: Could not open boot sector file "C:\path\toboot\etfsboot.com"

Error 3: The system cannot find the path specified.

When I click on etfsboot I get the following " This app cannot run on your PC. To find a version for your PC check with the software publisher"

Not sure where to go from here....

I am not sure if I have installed the right Assessment and Deployment Kit and Windows PE.

My computer has Windows 10 Pro, Version 22H2 installed, and

Windows feature Experience Pack:1000.19041.1000.0 on a 64-bit computer with 64-bit operating system.

The 2023-05 Cumulative Update for windows 10 Version 22H2 for a 64-bit operating system (KB5026361) has been installed.

When I look at the ADK downloads in lists Windows 11 22H2, (but not Windows 10 22H2).

Then it lists ADK for Windows 10, version 1903, and the Windows PE add-on for ADK, version 1903. This is what I have downloaded, but was this correct?