Vertex drawings or models do not open when double-clicking the file.

Problem
You want to open Vertex Viewer (or another Vertex application) by double-clicking a Vertex model or drawing file in a folder. The files open correctly if you first start Vertex and then choose Open file from the program, or if you drag the file onto the Vertex desktop. However, double-clicking only produces an error message, and the program does not start.

Solution
Starting from Windows 7, the user interface only allows very simple file extension associations, so an additional tool is needed for proper association. One such tool is:

http://www.nirsoft.net/utils/file_types_manager.html

The association should be set up as shown in the example image below: