The setting your "experts" are "unaware of" is called Filter, its a pretty standard way of defining file-extensions which are selectable or even preselected. Simply put in All files (*.*)|*.*
as the first element in the string and you're good to go, the order in this string will be the order in which elements in the dropdown are available / preselected - you can also change the preselection with FilterIndex
Also : this is a question about programming, not systems integration / administration.