[el_barto]

Yo intente hacer lo siguiente pero ni aun asi me deja de pregunta esa maldita ventana:

begin
Application.Initialize;
Application.CreateForm(TDataModule2, DataModule2);
Application.CreateForm(TForm3, Form3);
if Form3.ShowModal = mrOk then
begin
form3.Free;
Application.CreateForm(TForm1, Form1);
Application.Run;
end;
end.

y en mi boton de conectar en mi form de password coloque

procedure TForm3.Button1Click(Sender: TObject);
begin
DataModule2.IBDatabase1.Params.Values['USER_NAME'] := Edit1.Text;
DataModule2.IBDatabase1.Params.Values['PASSWORD'] := Edit2.Text;
try
DataModule2.IBDatabase1.Open;
except
MessageDlg('error de logueo', mtwarning,[mbyes,mbno],0)
end;
if DataModule2.IBDatabase1.Connected then
begin
ModalResult := mrOk;
end;
end;
end.