[NumLock]

Код:

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    procedure FormCreate(Sender: TObject);
...
procedure TForm1.FormCreate(Sender: TObject);
begin
  SetCurrentDir('c:\Windows\System32\');
  SendMessage(ListBox1.Handle, LB_DIR, $3f, Integer(PChar('*.dll')));
end;