Since you are using the HD version you will not find conquerors to be uninstalled anywhere on your PC (unless you have the classic version installed as well).

You will need to uninstall the HD version and the compatibility patch and then start off fresh with the clean install guide.
lightApprentice wrote:
I never install games on C drive and I selected proper game directory manually as diag tool requested.

Install the game in it's default directory in C drive.

P.S: Before you install the compatibility patch ensure the game is working fine on Steam. Furthermore, do not use any third party tools for the conversion process and stick to the clean install guide.

If it still does not work, try enabling/disabling window mode in your game room.