Noise coming from starter?



I have a 2000 Ford Expedition with 80,000 miles on it. It appeared the battery is dead. So when I hooked the battery cables up to jump it and before I even attempted to start it, I heard a couple short grinding sounds. I verified that I had the battery cables hooked up correctly, and went ahead to start it. It turned over and started, but then these short, loud grinding noises continued intermittently. Any ideas?