I checked your message and the error screen shots. Thank you for the detailed description of the problem. I see that you receive this error message in Disk Management console:
"The operation failed to complete because the Disk Management console view is not up-to-date. Refresh the view by using the refresh task. If the problem persists close the Disk Management console, then restart Disk Management or restart the computer."
Try using the below mentioned steps and see if the issue is fixed:
1. Click Start and type Diskpart in the search box.
2. Right-click diskpart in the search results > click Run as administrator.
3. Once diskpart loads type list volume, press enter.
4. You should notice that you will see your 2 TB Western Digital Hard Drive, it should not show a drive letter assigned to it.
5. Type select volume 1 (replace 1 with the volume number assigned to the Hard Drive in question).
6. Type assign letter Z (replace Z with the letter that you want to assign to it).
Do reply with results.