Which way is a better procedure to open an existing Civil 3D drawing-by Clicking the C3D icon to open an empty file, and then using "Open" tool in the in the Application Menu to open the desired existing drawing OR by going into the Windows Explorer and opening the drawing from its host drive? Is there really any difference between the two procedures?
It doesn't matter in the slightest. Except if you have a habit of switching profiles, or if you use other AutoCAD software like Civil 3D as AutoCAD, plain old AutoCAD, AutoCAD Map...anything that opens DWG files. In this case, start the program first then open.
The difference is this: double clicking a DWG file in Explorer use the AutoCAD Launcher application. This determines which AutoCAD program and which Profile was loaded the last time you opened an AutoCAD product. It then opens that program and profile combination.
Matt Kolberg Cansel - Autodesk Division http://www.cansel.ca/