Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

procedure ShowMultiColumns(FileListBox: TFileListBox; bValue: Boolean);
 begin
   with TDirectoryListBox(FileListBox) do
   begin
     Columns := Ord(bValue) and (Ord(bValue) and 1);
     SendMessage(Handle, LB_SETCOLUMNWIDTH, Canvas.TextWidth('WWWWWWWW.WWW'), 0);
   end;
 end;

 {Example:}

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   ShowMultiColumns(FileListBox1, True);
 end;