Tutorials

The selected disk is not a fixed MBR disk

This error appears when trying to mark a partition on a disk as active, either through Disk Management or DiskPart. The error message appears as follows:

The selected disk is not a fixed MBR disk.
The ACTIVE command can only be used on fixed MBR disks.

This problem indicates that the disk on which the partition that you want to mark as active is located as a GPT disk (GUID partition table). This is closely related to the UEFI boot specifications rather than the BIOS and this boot method does not recognize a concept such as the active partition.

There are several things you can do to solve the problems simply by following the methods we have prepared below..

What causes the error message “The selected disk is not a fixed MBR disk”?

Identifying the correct cause of the problem is one of the most important steps in solving it.. Take a look at the list below to see the most common causes and how to fix them:

The problem is usually simply due to the fact that the drive on which you want to add a primary partition or activate a partition is formatted as GPT, which does not support these functions. Changing its format to MBR should solve the problem.
Bootloader problems can also cause the error message to appear and this can be resolved by running various useful commands to fix it.
If your boot mode is set to UEFI, you may want to consider changing it to Legacy, as this has solved the problem for many users.

Solution 1: convert disk to MBR

Since a disk formatted as GPT does not recognize a concept as active partition, you can simply convert it from disk to MBR, what will solve the problem effectively. After that, you can create a primary partition and mark it as active. However, make sure to back up the data to disk, since they will be deleted.

You can use the command prompt and DISKPART to clean the disk and convert it to MBR easily.

If your computer system does not work, you will need to use the installation media used to install Windows for this process. Insert the installation disc you have or just created and start your computer.
You will see a window Choose your keyboard layout, so choose the one you want to use. The Choose an option to navigate screen Problem solving >> Advanced Options >> Symbol of the system .

Command prompt in advanced options

In this command prompt window, just type »diskpart» on a new line and click the Enter key to run this command.
This will change the command prompt window to allow you to run various Diskpart commands. The first one you will run is the one that will allow you to see the complete list of all available volumes. Type this and make sure to click Enter after:

DISKPART> list

Make sure you choose your disc carefully, according to the number assigned in the volume list. Let's say your number is 3. Now run the following command to select your USB drive:

DISKPART> select volume 3

A message should appear saying something like “The volume 3 is the selected volume”.

Select the correct volume

Note: If you are not sure which drive number belongs to your USB device, the easiest way to do it is to check its size in the right panel.

To clean this volume, all you need to do is type the command shown below, then click the Enter key and be patient for the process to complete. The process should now be successful for a change. The command set will also convert the disk to MBR and we hope it will solve the problem.

Clean up
Convert the MBR
Departure

Solution 2: fix boot manager

Going over essential bootloader-related commands is always a nice and easy way to start troubleshooting.. There are several methods that you must run in a particular order to restart the bootloader service, which is directly responsible for managing the drives connected to your computer.

If your computer system does not work, you will need to use the installation media used to install Windows for this process. Insert the installation disc you have or just created and start your computer.
You will see a window Choose your keyboard layout , so choose the one you want to use. The Choose an option screen will appear to navigate to Troubleshooting >> Advanced Options >> Symbol of the system.

Command prompt in advanced options

If you have no problems with the system, you can use the windows interface to access this screen. If you are using Windows 10 on your pc, there is another way to access advanced computer startup. Use the Windows key combination + I to open Settings or click the Start menu and click the gear key at the bottom left.
Click Update & Security >> Recovery and click Restart now option in advanced startup section. Your PC will proceed to restart and you will be prompted for the advanced options screen.

Restart now in Settings

Click to open command prompt from advanced options screen.
The command prompt should now open with administrator privileges. Type the command shown below and make sure to hit Enter after.

bootrec / RebuildBcd
bootrec / fixMbr
bootrec / fixboot

Later, close command prompt and choose Restart option. Check if the problem has disappeared.

Solution 3: disable UEFI in BIOS

How GPT is closely related to UEFI boot mode, you should try to disable UEFI from the start menu and change it to legacy. This has solved the problem for some users. Be sure to follow the instructions carefully!!

Turn on your PC again and try to enter BIOS setup by pressing BIOS key when system is about to boot. BIOS key usually appears on boot screen, saying “Press ___ to enter setup” the something similar. There are also other keys. The usual BIOS keys are F1, F2, Of, etc.

Press __ to run the installation

Use the right arrow key to choose the Security menu when the BIOS setup window opens, use the down arrow key to select the Safe Boot Settings option and press Enter.
Before you can use this menu, a warning will appear. Press F10 to continue to the secure boot settings menu. The Secure Boot Settings menu should open, so use the down arrow key to select Safe Boot and use the right arrow key to change the setting to Disable.

Disable Secure Boot in BIOS

Now is the time to change the boot mode from UEFI to Legacy. The boot mode option you will need to change is on different tabs in different manufacturers' BIOS firmware tools and there is no single way to find it. As usual, is in the home tab, but there are many names for the same option.
When you locate the Boot Mode option in any area of the BIOS setup screen, navigate to it and change its value to Legacy.

Switch from UEFI to Legacy Mode