Moving / recreating EFI partition

dkaplowitz said:

THank you for this - I'm not 100% clear on all of it though and I'd really rather not destroy my data (although I am backed up) so if anyone can answer the questions below in red I'd be grateful!
many thanks, David

diskpart
list disk (it will list all drives. Identify the NEW drive number)
select disk n (replace n by the NEW drive number obtained with list disk) This is to select the NEW drive that has no EFI partition
list partition (will list all partitions on the NEW drive. Find out the Windows partition number m )
select partition m (replace m by the Windows partition number obtained with list partition). You have selected the new drive with the select disk # command . This is to select the Windows partition on the NEW drive
shrink desired=100 (this is to shrink the Windows partition in 100M to be able to create a new partition)
create partition efi size=100 (this will create a EFI partition on the space created above)
format quick fs=fat32 (will format the EFI partition created above as Fat32)
assign letter=s To assign a letter S: to the EFI partition created above
list partition (will list all partitions on the new drive. You should have now an EFI partition after the Windows partition)
list volume Note: Note the volume letter where the Windows OS is installed. It will list all partitions with the corresponding letters on ALL drives. You have to find out what letter is assigned to the Windows on the NEW drive. If you're running Diskpart from Windows on the NEW drive, the Windows partition on the NEW drive will be C:. If you're running Diskpart from Windows on the OLD drive, the Windows on the NEW drive partition will be something other than C:.
exit

bcdboot X:\windows /s S: /f UEFI
Note: Replace "X" with the volume letter of the Windows OS partition. [X is the drive letter of the Windows partition on the NEW drive fond above]

Welcome to the Forums dkaplowitz.

See explanation on the commands above.
On a UEFI-GPT boot able drive you should have a EFI partition where the boot managers are (you can have one or more boot managers if you have multi boot).
If you have another UEFI-GPT boot able drive and you don't disconnect while you installing Win (7, 8.x, 10 or 11) on a NEW drive, the installation wizard will find a EFI partition on the OLD drive and install the boot manager of the NEW drive on the EFI partition of the OLD drive. The consequence is that the NEW drive isn't self boot able as you need the OLD drive to boot the NEW one.
The solution is to create a EFI - 100M Fat32 partition and load it with the boot manager.

diskpart
list disk
select disk # Note: Select the disk where you want to add the EFI System partition. [THIS IS THE NEW 1TB DRIVE WHERE THE CURRENT SYSTEM RESIDES BUT WITHOUT THE EFI PARTITION CORRECT? AND I GET THE DISK NUMBER FROM DISK MANAGEMENT CORRECT?] Yes the Disk Number as shown in above command that corresponds with the new 1TB Drive
list partition
select partition # Note: Select the Windows OS partition (# number) or your data partition. [IS THIS THE OLD SYSTEM DRIVE WHERE THE EFI PARTITION CURRENTLY RESIDES? THIS IS CONFUSING TO ME!] select the OS Partition Number as found on the new 1TB Drive
shrink desired=100
create partition efi size=100
format quick fs=fat32
assign letter=s [I'm ASSIGNING s to the new DRIVE?]No, But to the Newly created EFI "Partition"
list partition
list volume Note: Note the volume letter where the Windows OS is installed. [I'M NOT CLEAR ON WHAT THEY'RE SAYING HERE] Again the Volume (Drive) Letter with the OS on the Now Reconfigured 1TB Drive
exit

bcdboot X:\windows /s S:
Note: Replace "X" with the volume letter of the Windows OS partition. [THIS IS MY C DRIVE CORRECT?]The volume may list as any Drive letter - depending on number of listed drives... Do not assume it is C

You created a EFI partition and S was assigned to that EFI Partition - the Volume Drive letter is the Windows OS that you want to make Bootable via that EFI Partition - this will make the New 1TB Drive contain its own Bootable Partition - and it should be set as the Primary (First) Boot Drive in the BIOS

In this video, i will show you how to create EFI partition from within Windows Recovery Environment.

It is always a good practice to make a disk image backup before you begin to play with the drives.