You must first accociate a File Type with this application! In Explorer Extra/Folder options goto File Types and add a command to a extension e.p. .txt Enter the path to this executable and check DDE, then enter a command (e.p. [open("%1")]) an application name: CPDDETest and an Action Name: System. Then start this Program and open a file in explorer. A MessageBox should now show the command (%1 is replaced with the file name)