Run ‘cmd’ and type ‘diskpart’ to enter the diskpart utility.
Now enter ‘list disk’ at the prompt like below.
DISKPART> list disk
Identify the right disk in the ### column and note it’s appropriate number. In order to ensure that your choice is correct it may be helpful to have a look at the disk management.
Now type ‘select disk n‘ (where n is the number of the disk that’s containing the EFI partition you wish to remove)
DISKPART> select disk n
Once you’ve selected, delete the GPT / EPI by the clean command, type “clean” and press enter.
DISKPART> clean
You’re done, finish by typing ‘exit’ to leave diskpart.
NOTE: The “clean” command nukes ALL partition information from the disk!