Because they are text files, you may be tempted to modify the .DLG file and the .H file directly. However, these two files are interdependent, and if you make a change to one, you risk creating a conflict with the other. Also, changes you make in the .DLG file won't become a permanent part of a dialog because the .DLG file is only written by the Dialog Editor, not read. The best way to modify a dialog is to load it into the editor and make the changes there.