Right. As in your example, E, and F don’t show up, but in your case I assume they are in use, just like “B” (floppy?), “C” of course is the boot drive, and I assume “D” is the DVD.
In my case, “F” became “G” (the 500 GB MX500 SATA drive), and “E” (the original C: drive before the 1st cloning) is in a different machine entirely now.
Oh! Oh, Ho-ho-HO!!
Reassigning the “ghost” drives new drive letters “Q” and “R” via the registry WORKED!
And... NOW Q and R are visible in Disk Management as reserved volumes. (The volumes were there before, but no drive letters were visible as assigned to them. don’t ask me why not — — boy, would that have saved some grief!)
Actually letters A thru F plus L M R V are all used for drives (B is for Bible).
I see you got them back. https://www.diskpart.com/articles/drive-letter-missing-4125.html helps with details. Did you make sure Select View > Show > Hidden items was allowed?