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

Users who encounter the error message "The selected disk is not a fixed MBR disk. The ACTIVE command can only be used on fixed MBR disk" when attempting to make a primary partition active with DiskPart may be experiencing this issue due to the disk type. The ACTIVE command in DiskPart is only compatible with fixed MBR (Master Boot Record) disks, not with GPT (GUID Partition Table) disks. To resolve this issue, users can try converting their disk from GPT to MBR using the DiskPart command "convert mbr" or by using a third-party tool like Qiling Partition Master.

If you're experiencing the error message, this article is here to help. It will explain why you're seeing this error and provide a solution, so you can get back on track.

The Reason Why This Problem Arises

If you encounter the error "The selected disk is not a fixed MBR disk" when trying to install Windows, it's likely due to the disk type being used. This error occurs when the disk is a GPT disk, which is a newer type of disk that doesn't use a fixed MBR (Master Boot Record).

The Reason Why The Selected Disk is not A Fixed MBR Disk Arises

Several possibilities would cause this "The selected disk is not a fixed MBR disk" problem. We list the most common two reasons below.

The partition is formatted as GPT

The active command only works on BIOS/MBR systems. It does not function properly on GPT systems, especially when installed in UEFI mode, leading to recognition issues by the computer.

Boot manager problem.

If the computer is booting incorrectly, it may display the error message. To fix this, the boot manager needs to be corrected.

If you're unsure about MBR and GPT, you can check out the article on MBR vs GPT for a detailed explanation.

How to Fix "The selected disk is not a fixed MBR disk"

Now that you know the reasons behind the error message, you can fix the problem with the solutions introduced below.

Method 1. Convert GPT to MBR

Since the active command only works on a BIOS/MBR system, converting the partition from GPT to MBR might solve the problem, but this would involve deleting the current volume and could result in data loss. Alternatively, you can use the DiskPart Command Prompt or Computer Management to convert the partition, but these methods also require deleting the volume.

To fix the issue of "The selected disk is not a fixed MBR disk" without data loss, we recommend using a third-party partition manager like Qiling Partition Master. This tool allows users to resize partitions, convert partitions from MBR to GPT or vice versa, and even delete partitions in Windows, making it a useful solution for various partition-related tasks.

To convert a GPT (GUID Partition Table) to MBR (Master Boot Record), download and launch the software on your computer, then follow the steps provided to initiate the conversion process.

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Click the GPT disk that you want to convert and click "More..." and select "Convert to MBR".

Method 2. Fix Boot Manager

To fix the Boot Manager, you'll need to access your Windows installation drive, which can be found on the installation DVD or on the drive where Windows is installed. If you can locate the installation drive or DVD, follow the steps below to resolve the issue.

Step 1. Boot your computer from the installation drive.

Step 2. Choose "Repair your computer" from the welcome screen.

Step 3. Head to Troubleshoot > Command Prompt.

Step 4. Type the following command:

bootrec
FixMbr bootrec
FixBoot bootrec
ScanOs bootrec
RebuildBcd.

And press "Enter" after each command.

Step 5. Wait until the operation is finished, remove the installation drive from your computer.

Step 6. Type exit and press the "Enter" button.

To troubleshoot the issue, restart your computer and check if it boots properly. If the selected disk is still showing as a fixed MBR disk error message persists, further troubleshooting is needed.

The Bottom Line

The "selected disk is not a fixed MBR disk" problem typically occurs due to a conflict between MBR and GPT partitions on your computer. Understanding the difference between these two types of partitions can help you resolve this issue. Qiling Partition Master is a useful tool that allows you to manage your partitions without data loss, enabling you to clone, format, and merge partitions as needed.

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