Seagate 1TB Expansion goes Unallocated?

[bluefire]

I'm having this 1TB Seagate Expansion External HDD which turned out to be not showing up on My Computer anymore from the past two-three days, I tried switching ports and connecting it to a different computer; None of them worked out.
Today, I looked up in the disk management and it shows Disk 2 : 931 GB as "unallocated". I can try making a new simple volume but I'm afraid of losing data. I'm a videographer/editor and got my clients videos on that drive.
I'm attaching some screenshots just to pass in a bit of more information.
Nothing shows up on My Computer :

Disk Management :

CMD DiskPart :

 

[DR_Luke]

if you don't want to lose your data, seek professional data recovery assistance before you make it worse.

 

[D_Know_WD]

Hi there bluefire,

Your safest bet would be to look for some professional help, as DR_Luke said.

Apart from that, you can use some partition recovery software, as it looks like the HDD has lost its partitions. If you manage to retrieve the data, make sure it is backed up and test the drive afterwards: http://www.tomshardware.co.uk/forum/282651-32-best-diagnostic-testing-utility

You should never keep your important data stored on at least one place.

Cheers,
D_Know_WD