1997 Jeep Cherokee 97 Jeep Grand Cherokee LTD - Won't Start

I have a 97 Jeep Grand Cherokee Ltd. Recently (3/07) the battery was replaced (due to not driving it throughout the winter). The car has not been "driven" since 9/07 so I went to start it back up yesterday. Unfortunately, everything appeared dead and it required a jump. When it finally started the engine sounded very loud and the exhaust was thick but everything finally settled down. During a quick trip around the block the car appeared sluggish, but drove reasonably well. I then put the car in park and left it in front of the house while I made room for it in the driveway. When I put the car in drive again, the engine and all the electrical systems seemed to shut off for a moment but then came back on. The process repeated itself when I put the car in reverse. Finally, I turned the car off (after running for around 15-20 minutes total). A few minutes later when I attempted to start the car again it wouldn’t start (the lights inside were completely off). I tried to jump the car but nothing happened. When I turned the key the lights dimmed and I could hear the car slowly trying to turn over. What do you think the problem could be?