I've been having a lot of fun upgrading my old G4 Powermac Digital Audio (CPU, video card, USB 2.0, RAM, DVR, etc.) and now its very satisfying to use. But I can't help wondering if I could make some use out of the space occupied by the worthless zip drive. Is it possible to install a second optical drive in this bay? On the other hand, this could also just be a symptom of compulsive upgrademania -- maybe I've spent enough on this thing already.