Problems using frm.show(this)

In my program when I open a new form, I new to do "show(this)" ir order to send the parent to the new form, to ensure it is open in the same display (when multi monitoring) with the instruction CenterToParent.

Thats run, but the problem is when I do it the new window is always in front of the parent window.

I give you here an application example, in which after load Form2 from Form1, form1 is always back to form2, although it has the focus.
http://193.145.251.126/pnp/files/ivzRpJBad/TestVentanas.zip



Anyone knows how to solve it?

Thanks