Check out the System.Windows.Forms.Screen class. Specifically the static function Screen.GetBounds() method.
It returns a rectangle that gives you the bounds of the screen that your form is on (it can take account of multiple monitors if you want to).
Once you have the bounds of the screen, you can set the location and size properties of your form.
I haven't tried it myself but it looks like it should work.
Regards
Jero