After doing a Hard drive shuffle in my PC case, I decided to use my spare 1.5TB HDD in a Western Digital case.
After having set the HDD in the Ext. case, it is now showing as 'Write Protected' in drive management. It doesn't appear at all in My Computer.
I have tried to move it pre-formatted in both NTFS & Fat32, as well as deleting the entire volume.
The drive operates normally when mounted in PC, and other drives work in External case.