As said before, all that rf shielding like the cages and cardboard you're talking about was simply to make the machine part 15 compliant of FCC rules that were supposed to keep home electronics from leaking signals that can cause interference to radio or tv reception.
since the computer is not sold new in stores anymore, i second the notion for taking off the cardboard rf shield. I've seen the one you are talking about, its got a shiny side to it and paper on the other side. it looks like it would be more effective in evenly cooking popcorn in the microwave oven.
just throw it away.