>How to I determine if a specific directory exist on the C: Drive

Lessee... the DIRECTORY() function is one way: IF DIRECTORY(cDirPathinVar)
ADIR(): IF ADIR(aTempArray,cDirPathInVar,'D') > 0

and the ever-popular Scripting.FileSystemObject's FolderExists method:

oFSO = CREATEOBJ('Scripting.FileSystemObject')
IF oFSO.FolderExists(cDirPathInVar)

This is far from a canonical list of ways to do this, but I figure one of the three should work for you...

The two native VFP mechanisms have quirks wrt LFNs that VFP mishandles (things with multiple . characters seem to cause problems as an example) and the Scripting.FileSystemObject requires you to have installed the VBSCRIPT engines, usually placed on the system as a part of the Windows Scripting Host install.