By Michael / Last Updated March 9, 2022

Can’t upgrade to Windows 10, help!

“Recently, I decided to upgrade my old Windows 7 computer to Windows 10. In the beginning, everything went normal. However, in the middle of the upgrading process, I was stopped by a prompt saying “Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks”. Does that mean I can’t use MBR with UEFI boot mode? How to fix it”

mbr error

Overview of MBR and UEFI

MBR, short for Master Boot Record, is the first physical sector of the first floppy or hard disk on the system read and executed by BIOS, at the end of the ROM BIOS bootstrap routine. MBR contains a small program deciding which partition is bootable and attempts to boot from it. An MBR disk usually supports 4 primary partitions or 3 primary partitions plus 1 extended partition. Meanwhile, if the MBR disk is a system disk, the boot mode of the motherboard must be Legacy BIOS or Windows won’t boot normally. So, what’s UEFI?

UEFI, short for Unified Extensible Firmware Interface, is a publicly available specification that defines a software interface between an OS and platform firmware. If the boot mode of your PC is UEFI, then, to boot into Windows successfully, the system disk must be in the GPT partition style.

So, can I use MBR with UEFI? Based on the description above, the answer should be “No!”.  To boot from an MBR disk, the boot mode should be Legacy BIOS instead of UEFI and the boot mode is UEFI, to let Windows boot normally, the system disk should be in the GPT partition style.

2 ways to convert MBR to GPT

When the boot disk is MBR while the boot mode is UEFI, then, you cannot boot your PC or finish Windows installation. To resolve this issue, one of the best ways is to convert MBR to GPT once for all. Generally, there’re 3 ways to get it done.

Use DiskPart

DiskPart, the replacement for its predecessor – fdisk, is a Windows built-in utility in Disk Management. With this program utility, users can perform different operations including partition deletion, partition conversion and MBR GPT conversion by inputting command lines. To use DiskPart for MBR to GPT conversion, do as follows.

1. Boot into Command Prompt and launch DiskPart.

2. Type “list disk” and hit “ENTER” to list all disks connected to your PC.

3. Type “select disk n” and hit “ENTER” to select the disk in MBR you want to convert.

4. Input “clean” and hit “ENTER” to delete all existing partitions on the hard disk.

Note: Since all partitions on the disk will be deleted, you’d better make a backup of important files first.

5. Type “convert gpt” and press “ENTER” to start the conversion

convert cmd

After completed, try rebooting your PC or restart Windows installation and check whether they go normal.

Try third-party MBR-GPT converter – convert MBR to GPT without data loss

Since DiskPart asks for partition deletion during the MBR to GPT conversion, you’ll suffer from severe data loss. In this way, it’s imperative to find another alternative. This time, I recommend AOMEI Partition Assistant Professional, a powerful and friendly software utility that helps deal with disk management. It’s able to convert the system disk between MBR and GPT without deleting any partitions. Meanwhile, other features including primary to logical disk conversion, NTFS to FAT32 conversion, and SSD secure erase are supported.

Is MBR compatible with UEFI? No! You have to convert MBR to GPT to work with UEFI. Thus, download the demo of the most powerful MBR GPT converter to have a try!

Download Demo Win 11/10/8.1/8/7/XP
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Step 1. Install and launch AOMEI Partition Assistant Professional. Then, right-click on the MBR system disk and select “Convert to GPT Disk”.

convert to gpt

Step 2. Hit "OK" to proceed.

ok

Step 3. To execute the pending operation, hit “Apply” where the screenshot shows.

apply

Change UEFI to Legacy

To resolve the Windows not booting issue or Windows installation failure mentioned above, besides converting MBR to GPT, you can change switch the boot mode from UEFI to Legacy as well.

1. Right after powering on your computer, keep hitting a certain key to enter the EFI Setup menu. Usually, the key should be Del for desktops and F2 for laptops. If you have no idea which key you should hit, just press Esc and it will give you a full menu where you can select “BIOS Setup”.

2. Under the Boot tab lies the option “UEFI/BIOS Boot Mode”. Now, use the arrow key to select “Legacy” as the boot mode.

3. Hit F10 to save the change and then, you can quit the interface and reboot your PC.

uefi to legacy

Conclusion

Can I use MBR with UEFI? The answer is no – an MBR boot disk must work with the Legacy boot mode and to work with UEFI, the disk should be in the GPT partition style. So, in this post, the best way to convert MBR to GPT without data loss – using AOMEI Partition Assistant Professional - is provided and meanwhile, you’ve also learnt to switch between UEFI and Legacy.

As for the AOMEI product, if you’re a Server user, you can no longer use the Pro edition. Nevertheless, you can try the Server edition that supports Server versions from the old 2003 to the latest 2022.