property FilterIndex : Integer;
Determines which of the file types in Filter
is selected by default when the dialog opens. Set FilterIndex to 1 to choose the first file type in the list as the default, or 2 to choose the second file type, etc.
Generally it is better to use FilterDefault
to choose a particular format such as JPEG or AVI.
Note: this setting is ignored if you have specified a filename or set a type for FilterDefault