My 1TB External Hard Disk Drive has been reduced to 31.9 GB after I downloaded the Win 10 Media Creation Tool

Use diskpart to clean the entire drive - this will mean you’ll lose everything on the drive.
Open cmd prompt/powershell with admin & type:
Diskpart & press enter
List disk then press enter
Select disc x where x is the number of the external hard drive you wish to clean.
Type Clean & click enter
Once completed type exit & click enter.
Then go to disk management under control panel & it should pop up stating the drive needs initialising/formatting, Choose to do so & it should then show the full capacity.
If not then try a third party software: EaseUS partition manager:
https://www.easeus.com/partition-manager/

Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.

Hi Imtiaz,

Since you have formatted your hard disk it may have lost its allocation properties and would be no longer visible with the other Hard Disk Drives in 'This PC'.

To make it visible you will have to follow the below mentioned steps: (make sure your external hard disk is connected)

1. Open Start

2. Type - Create and format hard disk partitions

3. Open it

4. At the bottom of the open program you should be seeing your external hard disk with a long black colored line

5. Right Click on it and Select 'New Simple Volume'

6. Thereafter a Dialog box should appear asking what kind of setting you would like to apply to your external hard disk, select accordingly (make sure to keep the File System to NTFS).

7. After clicking apply you should be able to see your external hard disk along with other hard drives in 'This PC'

Thank You