How to Fix The Selected Disk is not a Fixed MBR Disk?

In this documentary I will tell you How to fix the selected disk is not a fixed MBR disk?

The error message “The selected disk is not a fixed MBR disk” indicates that the commands you are trying to use are suitable only for MBR disks and that you are working with a GPT disk. The “Active” command you are trying to use is not applicable to a GPT disk.

How to fix the selected disk is not a fixed MBR disk?

The error message “The selected disk is not a fixed MBR disk” indicates that the commands you are trying to use are suitable only for MBR disks and that you are working with a GPT disk. The “Active” command you are trying to use is not applicable to a GPT disk.

This error usually appears under several circumstances. It usually appears when you try to set a primary partition as active on a GPT disk, a concept that is not recognized by GPT (GUID Partition Table). Also, if the boot manager or BCD (Boot Configuration Data) store is having issues, this error message is likely to appear.

With the causes explained, let’s explore the solutions.

1. Repair BCD Store 

The computer firmware uses the BCD store at startup to locate Windows for booting. If the BCD store is corrupted or missing, you may see related error messages. Using BCD commands can help repair a corrupted BCD store by copying the boot files from the Windows system drive and rebuilding the lost BCD store, which may resolve the issue.

• Insert a bootable Windows USB. Use this guide if necessary.
• Go to boot options by pressing Delete and select the USB drive.
• Boot from USB, select your language and click Next.
• Choose Repair your PC.
• Select Troubleshoot and then Command Prompt.
• Determine the system drive and partition using: diskpart list disk select disk 0 list volume Note: Replace “0” with your specific OS disk number.
• Assign a letter to the FAT32 volume:assign letter=z Exit diskpart using exit.
• Run the BCD command replacing y with your OS drive and assigned letter: bcdboot /I /s /f For example: bcdboot D:/Windows /I en-us/s Z:/f All Check if the error is fixed.

2. Convert GPT to MBR disk 

Converting GPT to MBR disk can solve "The selected disk is not a fixed MBR disk" error, but all data on the disk will be erased. Please backup important files first. Non-OS drives are easy to convert using Command Prompt or Disk Management tools. If the GPT disk has your OS on it, you will need to reinstall Windows and switch to BIOS legacy mode, as MBR supports BIOS booting, while GPT is for UEFI.

• Type these commands. diskpart list disk select disk (e.g. select disk 0) convert MBR 
• Now, the MBR commands will work without any error messages.

3. Fix Boot Manager

 If the Boot Manager is not working properly it can cause this error. Boot Manager is important for turning on your computer because it controls the entire boot process and directs the system to the correct partition. Running the commands to rebuild the BCD configuration data, the MBR, and restore boot functionalities can make the boot process more reliable, fixing any boot errors.

• Open Command Prompt as Administrator.
• Type cd /d C:\Windows\system32 and press Enter.
• Run the following commands to repair the bootloader: bootrec /RebuildBcd bootrec /fixMbr bootrec /fixboot Check if the problem has been resolved.
• If the above methods have not worked, you can change the BIOS mode from UEFI to Legacy by following this guide. First, you will need to convert your GPT OS disk to MBR using the second method and then you can reinstall Windows on the MBR disk which will fix the error.

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