add a button to Form1 and in the handler of that button click add:
Form2 f2 = new Form2();
this.WindowState = FormWindowState.Minimized;
f2.ShowDialog();
if you want to maximize again try adding
this.WindowState = FormWindowState.Minimized;
after f2.ShowDialog. (if that doesn't work you'll need to fire an event that Form1 catches.
to start Form2 Maximized use the same principle
f2.WindowState = FormWindowState.Maximized;
It might not be 100% correct, but should get you on your way.
Hope this helps.