The connector on the circuit board isn't proprietary, it's a standard 3.5 connection, the board attaches with 2 screws, easy to remove and swap a different drive.
If you took the original drive out and want to replace it with a different drive, you have to install the WES driver and then download and run the Windows quick formatter program from Western Digital.
There might be another way such as a few of the linux boot cd partition tools like gparted, but this is the easiest way.
I found the My book 2tb drives on close out at Staples for $41, bought 4 of them just to steal the drives for other purposes and I'm now using the Western Digital cases for extra storage with s few old 500 and 300 Gb drives I had laying around.
My only mistake was that I wished I bought all they had, as you can't find a new Western Digital 2 Gb green drive for $41!!!