I have a 2TB Western Digital MyBook Essential External Hard-disk. I wanted to use the Hard-disk as an internal hard-drive for my PC running Linux Mint. So, I dis-assembled it, and took out the SATA Hard-disk. Now, I assembled it into my PC using the SATA port. 

The hard-disk's partition are not recognized now. In GParted. it shows as follows: 

[![enter image description here](https://i.stack.imgur.com/lMObb.png)](https://i.stack.imgur.com/lMObb.png)

I then took out the hard-drive and assembled it back into its external USB case. It is recognized just fine now. 

I am stumped. What might be causing this? The hard-drive is recognized just fine in its external USB case but NOT when connected through internal SATA.