Simply connect your HDD to computer. If it run any application (i.e. WD Unlocker) then disable it or remove it.
It may be possible that there is a virus in your HDD and it is running automatically while you are connecting to any device. So it is better that you scan it.
Some time it takes lots of time to detect. It is totally depending of number of files present in your HDD.
One more things to remember is that file system of the HDD must be NTFS
If this doesn't work than backup your data and format your HDD and try again without any data.
Hope this helps