Undo all the thumbscrews around the hot plug cage. Open the side panel, and
roughly in the middle of the open cavity, is a white semi-circular pull
handle with a little screw in it. Give it a tug so it comes out about an
inch, and give the front of the cage a pull. It will slide out, and you can
undo the screws around the CD ROM drive and then you can replace it in the
usual way. Be gentle!