You also need to inherit your class from the 'System.Windows.Forms.Form'
class which will automatically activate Form Designer support (very nice
detail).
Remember to add a reference to the System.Windows.Forms dll.

This is the minimum code for a Windows Application:

--- Code --------------------------------
using System;
using System.Windows.Forms;

namespace MyNamespace
{
   class MyClass : System.Windows.Forms.Form
   {
       [STAThread]
       static void Main()
       {
           Application.Run( new MyClass() );
       }
   }
}
------------------------------------------

(To show what you created in the Form Designer you need to call
InitializeComponent() from the class constructor)

good luck, Teis