If you have transferred the data off that E drive, then you can use Command Prompt to delete all partitions on that drive, please note, this process will wipe the whole drive..
Open Command Prompt by right clicking its icon and select 'Run as Administrator'.
Run this command and hit Enter:
diskpart
Run this command and hit Enter:
list disk
(Make note of the disk number you want to wipe and enter it into the next command - replace X)
Run this command and hit Enter:
select disk X
Run this command and hit Enter:
clean
Close Command Prompt, then please provide a screenshot of that disk in Disk Management.