What to do if you have this error message "The file being opened for reading does not exist"?

If you have this message you need to follow these points:

In the Start-in menu, right click on the HyperMesh icon > More > Open File Location
Right-click on the icon > Properties
In the "ShortCut" tab, check that the directory listed next to "Startin" is a valid directory. If not, enter a vlaid directory.
The default value is "%USERPROFILE%\Documents" without quotations marks. "%USERPROFILES%" is an alias for "C:\Users<your_username>".
Click OK. Reopen HyperMesh.