How can I create a hidden application?

begin
  Application.Initialize;
  Application.ShowMainForm:=False;
  Application.CreateForm(TMainForm, MainForm);
  Application.Run;
end;

In this example, the main form does exist, but will not be visible. For other forms than the main form, you can simply at design time set their visible property to false. However, for the main form, you need to set the ShowMainForm property of the Application object.

Source: www.guidogybels.net.