To compare the activities (the progression-free survival, the incidence and severity of toxicities, and reversibility of toxicities) of erlotinib to that of platinum-based therapy in NSCLC. A sequential therapy design has been chosen such that all patients will receive any potential benefits of both platinum-based and erlotinib therapy, without compromising survival by denying anyone potential therapy. With this design, progression-free survival will be tracked by treatment received. However, data will be generated which will show the safety and efficacy of erlotinib in the frontline setting (alone and with historical comparison to platinum-based therapy), as well as the potential safety and activity of platinum-based therapy in the "second-line" (post-erlotinib) setting. This should allow for the demonstration of the relative median time to progression, objective response and clinical benefit rates, overall survival, and safety and tolerability of erlotinib and platinum-based therapy in both the frontline and second-line settings in NSCLC. Also, in this fashion, the treatments serve as controls for each other, as well as being compared to historical controls; in the first line treatment portion, the platinum-based regimens serve as the historical control, while in the second-line setting, erlotinib serves as the historical control arm.