Press Windows key + X
Click Disk Management
Is a drive letter assigned to the drive?
Right-click the partition or drive that you want to change, and then click Change Drive Letter and Paths.
Do one of the following:
•To assign a drive letter if one has not already been assigned, click Add, click the letter that you want to use, and then click OK.
•To change a drive letter, click Change, click Assign the following drive letter, click the letter that you want to use, and then click OK.
•To remove a drive letter, click Remove, and then click Yes to confirm that you want to remove it.
Change, add, or remove a drive letter
Option 2:
Open Start, type: CMD
Right click CMD
Click Run as administrator
At the command prompt type:
takeown /F (external drive letter) and press Enter.
Type : CACLS (external drive letter) /G Administrator:F and press Enter.
Restart the computer and test the issue.