You can't change things like the menubar etc after the window has been opened so you have to use the window.open(arg1,arg2,arg3) method.
argument 1 is the filename, argument 2 is some kind of reference to the window, rarely use it so I don't remember...
argument 3 is where you specify what menus you want to show. I'm sure you can find out what to write in there by looking at a Javascript reference somewhere. Microsoft Script Editor has a very good help section too..