setting the Application.MainFormOnTaskbar to False will indeed work, But (I forgot to mention, my bad) I am experimenting with a very old Delphi language and thus setting the Application.MainFormOnTaskbar to False won't work. I instead found a workaround (created a tiny procedure):

procedure TFRMlogin.FRMshow(Form: TForm);  
begin  
SetWindowLong (Form.Handle, GWL_EXSTYLE,GetWindowLong (Form.Handle, GWL_EXSTYLE) or WS_EX_APPWINDOW) ;  
end;