.... And this will show Form2, and Hide Form1
Code:
		static void Main() 
		{
		// Instantiate a new instance of Form1.
		Form1 f1 = new Form1();
		Form2 f2 = new Form2();
      // Display a messagebox. This shows the application 
      // is running, yet there is nothing shown to the user. 
      // This is the point at which you customize your form.
      System.Windows.Forms.MessageBox.Show("The application "
         + "is running now, but no forms have been shown.");
      // Customize the form.
      f1.Text = "Running Form";
      // Show the instance of the form modally.
      f1.Visible = false;
	  f2.ShowDialog();
		}