easy,in the properties inspector for the main form, set the "IsMdiContainer" property to true. then create a new form and call it Form2 (the default value, used for the sake of this example) in the load event of the first form (Form1), paste this code. Form2 Form2 = new Form2(); Form2.MdiParent = this; Form2.Show(); the Form2 now cannot escape the parent, which is an Mdi, or multiple document interface form.