If you want to convert a disk from GPT to MBR or vice versa, you need to wipe out the disk content first. This guide will describe how to convert the disk type from GPT to MBR or from MBR to GPT. You can do this either using GUI or by using diskpart.
Backup your data before you start.
Step 1. Press windows key + X and click disk management.
Step 2. Right-click any partition on the drive that you want to change and click delete volume or delete partition to wipe out the data.
Step 3. Repeat the step 2 for all partitions.
Step 4. Locate the disk. Right-click it and click convert to GPT disk (If it is already GPT, click convert to MBR).
Now you can add volumes to the disk again.
Backup your data before you begin.
Step 1. Open command prompt with elevated privileges and run:
Step 2. Note down the disk number you want to convert after executing above command.
Step 3. Execute the following commands (Replace # with actual disk number)
select disk #
Step 4. To convert the disk to GPT, execute the following command:
Step 5. To convert the disk to MBR, execute the following command: