Double clicking on some .form files crashes Preform (on two of my Windows 8.1 machines).
It only happens with some files, i’m not sure what’s special about them.
Opening them from within Preform works perfectly fine, though.
I can provide an example file if you need one.
Isn’t this just a case of Windows not understanding what application to use to open the file? Did you try to associate the extension with the Preform application?