I Converted My HDD from MBR to GPT Using CMD Now Windows Won't Boot

Hello people, I converted my Hdd to GPT using the command, and now I can't boot up Windows 10 again. It just comes up saying, 'Reboot and insert boot media in the selected boot device,' and I can only go into BIOS. My pc is 32-bit with 8gb ram(only 2.96 usable). Can I redo the commands with an installation disc or usb recovery? If not, do any solutions?

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Roxanne· Answered on Jul 31, 2023

You may receive the message "Reboot and insert boot media in the selected boot device" when boot your computer after converting MBR to GPT. Don't know what to do? Follow up and learn the complete guide on how to fix it.

According to your description, there are mainly two possibilities for your case. One is you convert the HDD to GPT but forget to change the BIOS mode from Legacy to UEFI. Another is you have damaged the Windows boot files during the disk conversion. Luckily, I will provide two reliable solutions to the mentioned situations.

Incompatible BIOS mode

A GPT disk partitioning scheme can only be supported by UEFI boot mode. Follow the easy steps to enable UEFI boot mode on your computer:

Step 1. Restart the computer and long-press the F2 key to enter the Boot Manager screen. (Different computers may have different enter keys for boot settings.)

Step 2. Head to the "Boot or System Configuration" unit and click "Boot."

Step 3. Under the "Boot" tab, choose "UEFI/BIOS Boot Mode" and press "Enter."

Step 4. Switch the boot mode from "Legacy" to "UEFI," press "Enter," and Press F10 to exit.

Further Reading: UEFI vs. BIOS: What's the Difference

Windows boot files deleted or corrupted

Converting the disk using diskpart will erase all the data on the original drive, including the Windows boot files, such as the boot loader. In this case, you need to prepare a Windows installation disk or USB as bootable media and use the automatic repair option to fix the problems.

Here is how to do so:

Step 1. Boot from the Windows installation disk or USB.

Step 2. Go to the install screen, and click "Repair your computer."

Step 3. Open Command Prompt and type the following CMD.

For Legacy BIOS users:

  • Bootrec /fixmbr
  • Bootrec /fixboot
  • Bootrec /rebuildBCD

For UEFI users: bcdboot C:\windows

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