By AOMEI / Last Updated November 20, 2019

What is an EFI partition?

The EFI system partition (ESP), a small partition formatted with FAT32, usually around 100MB, this is where the EFI boot loaders and applications used by the firmware at system during start-up are stored. If your hard drive is in the GUID Partition table (GPT) partition style, it will automatically generate an EFI system partition after you have installed your operating systems. Both Windows and Mac operating systems are supported.

You normally can’t view the EFI partition through File Explorer (or Finder for Mac OSX) as it doesn’t have a drive letter assigned to it and if you accidentally manage to find and delete the partition, then your system will be unbootable. In order to protect the EFI partition, Windows will attempt to prevent you from deleting it. So, in the circumstances where you still wish to delete the EFI partition, what can you do?

How to delete it?

As we mentioned above, the EFI partition is essential if you want to be able to bootup your operating system that you have installed on your internal hard drive. However, if you have an external hard drive rather than internal one, you do not require an EFI partition to boot from the drive. Users who have created an EFI partition on a Mac and now want to install Windows will need to delete the original EFI partition and generate a new one. To delete the original EFI partition, you can use AOMEI Partition Assistant Pro, a specialist third party partition manager that will enable you to delete any partition without losing data on others.

To delete the EFI partition using AOMEI Partition Assistant follow the below steps:

1. Install and run AOMEI Partition Assistant Pro.

2. Connect either a USB drive or CD to your computer and click Make Bootable Media. Follow the wizard to create a bootable disk.

Make Bootable Media

3. In the main window, right click on the EFI partition that needs to get rid of and select Delete Partition.

Delete EFI System Partition

4. In the pop out window, click “OK” to confirm.

Delete EFI Quickly

5. The EFI partition has now become unallocated space, and you can add this unallocated space to any of the existing partitions by using the Merge Partitions function. The program has not yet made any permanent changes to your hard drive, if you’re happy to proceed you need to click Apply to save the changes.

Apart from deleting the EFI partition, AOMEI Partition Assistant has many useful features that the in-built Windows Disk Management doesn’t. AOMEI Partition Assistant has the ability to convert disks between GPT and MBR without losing any of your data, create bootable media, move partitions, migrate operating systems, recover partitions, and more!

How to create EFI partition?

In order to boot Windows on a GPT disk we know that the drive must contain an EFI system partition and a Microsoft Reserved Partition (MSR). If you delete the EFI partition on the system disk by mistake, then Windows will fail to boot. On occasion, when you migrate your OS or install it on a hard drive, it may fail to generate an EFI partition which causes the system to be unbootable. So, what can do we if when this happens?

In this case, you will need to create a new EFI partition and then install an EFI boot loader in order to make the hard drive bootable. If you happened to lose your EFI partition or didn’t generate a new one, you can follow the steps below to create one.

1. Boot your computer from a Windows installation disc or recovery disk. Press Shift+F10 during the setup to enter command prompt.

2. Run the commands below to shrink the partition to free up some unallocated space.

Diskpart

List disk

Select disk X (X represents the disk number of the disk that requires an EFI partition)

List partition

Select partition N (N represents the partition number of the partition that needs shrinking)

Shrink desired=500 (shrink the partition by 500MB)

3. Then you can create EFI partition out of the 500MB unallocated space using the command below:

create partition EFI size=200

format quick fs=fat32 label="System"

create partition msr size = 128

4. After those two partition have been successfully created, use the commands below to install boot loader and other applications needed.

bootrec /fixboot

bcdboot c:\Windows /s b: /f ALL

On an EFI-only system, the last two options don’t need to be included, and the command should read "bcdboot C:\Windows".

5. Reboot your computer to see if it is now bootable.

If your computer fails to boot because of a missing EFI system partition, you can use the above method to recreate it, and then your Windows system should boot as normal. Even though this will not cause data loss, it is also recommended to create a disk backup before you make any changes.