Recreating EFI for Windows

Boot Your PC and Prepare for a Dual Boot (Windows 8/8.1/10)

A while ago as I was playing around with my dual-boot system, I accidentally deleted the EFI partition and had to figure out how to restore my windows installation. below is the steps i took to recover.

What You’ll Need:

• A bootable USB drive or DVD containing your desired Windows 8/8.1/10 installation media.
• Some knowledge of your computer’s BIOS settings (consult your motherboard manual if needed).

Steps:

1. Boot from Installation Media:

• Insert your Windows installation media and restart your computer.
• During startup, you might need to press a specific key (usually Del, Esc, F2, F10, or F9) to enter the BIOS settings. Refer to your motherboard manual for the exact key.
• In the BIOS, locate the Boot Options menu and set the installation media (USB drive or DVD drive) as the first boot device. Save the changes and exit BIOS.
• Your computer should now boot from the installation media.

2. Open Command Prompt:

• On the first screen of the Windows installation process, press Shift+F10 to open a command prompt window.

3. Prepare the Partition (Important: Back up your data before proceeding):

• In the command prompt window, type the following commands one at a time, pressing Enter after each:

diskpart
list disk

• Identify the disk number where you want to create the EFI System partition (usually Disk 0).

select disk # (Replace # with the disk number)
list partition

• Identify the partition number you want to shrink to create space for the EFI partition (typically your Windows OS partition or a data partition).

select partition # (Replace # with the partition number)
shrink desired=100  (Replace 100 with the desired size in MB for the EFI partition)

• This command shrinks the selected partition by 100 MB (adjust the value if needed).

create partition efi size=100
format quick fs=fat32
assign letter=S
list partition
list volume 
exit

• This creates a new EFI partition of 100 MB formatted as FAT32, assigns it the drive letter S, and lists all partitions and volumes.
• Note down the volume letter where your Windows OS is installed (usually C:).

4. Configure Boot Manager

• Type the following command and press Enter:

bcdboot X:\windows /s S:
# Note: Replace "X" with the volume letter of the Windows OS partition.

• Replace “X” with the volume letter of your Windows OS partition (noted in step 3).
• This command copies the boot files from your Windows partition to the newly created EFI partition (S:) and sets it up for booting.

5. Finalize and Restart

• Type exit and press Enter to close the command prompt window.
• Remove the Windows installation media and restart your computer.

6. Set Boot Order in BIOS:

• Your computer should boot normally. However, you might need to access your BIOS settings again to ensure your primary hard drive/SSD is set as the first boot device. This ensures your existing operating system remains the default.