Plug in the external USB hard drive.
Right mouse click on My Computer
Left click on Manage
Double click on Storage
Double click on Disk Management
Disk 0 is Hard Drive Partitions.
Disk 1 will display the SIZE of the external device with no name
Right mouse click the blue colored bar on Disk 1
Left click on Mark Partition as Active
Left click on Change Drive Letter and Paths
Right click the “Add” button - Right click OK
Following is the end result. The external USB device should now have a drive letter.