


I tried using Diskpart again to assign them the same letters, but it tells me that those letters are already in use. I tried plugging the drives back in so I could remove the letter, but the EFI partitions on those drives did not get drive letters (which is the normal behavior).

Now I have two phantom drive letters S: and T: that are now permanently mapped to my PC even though I no longer have the hard drives in question attached. I had to update the BCD store on them so I used Diskpart to assign letters S: and T: to the EFI partitions on the drives. I recently attached two GPT-formatted USB hard drives to my Win10 workstation.
