Gladly inform you that I did manage to remove the drive letter, though I had my heartbeat paced quicker in doing so
And assigned the letter to another drive.
I restarted it twice to Win 7 and WDP alternately and did few things with it. Now it disappear from both system (hidden as it supposed to be).
You are all helpful friends
Now I'm back to normal heartbeat and breath normally.
Here is the screenshot