Solution
There is a VI in
Functions Palette » File I/O » Advanced File Functions called "File Dialog." This VI calls a File Open dialog box without opening a file, and then passes out the complete path of the file selected by the user. This VI allows you to specify a start path for the dialog. You can insert it into your program, providing any initial start path, and wire the path output from the File Dialog VI into your main file I/O VIs, as shown below: