Removing a Drive Letter from a Volume

Open Command Prompt as Admin
Run: Diskpart
DISKPART> list volume

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 System Rese NTFS Partition 500 MB Healthy System
Volume 1 C NTFS Partition 223 GB Healthy Boot
Volume 2 D SSD NTFS Partition 894 GB Healthy
Volume 3 E NTFS Partition 698 GB Healthy
Volume 4 F My Passport NTFS Partition 1862 GB Healthy

DISKPART> select volume 4
Volume 4 is the selected volume.

DISKPART> remove
DiskPart successfully removed the drive letter or mount point.