1996 Ford Taurus wont turn over

Battery was dead jumped to start not enough juice for car to stay running went to pull out at stop sign car shut off. Jumpped car again to start all lights on dash lit up pulled key and still all lit upnow car wont turn over or any thing

updated 3/22/2010
The flex pipe was loose and making noise everyone says the motor is locked, because of flex pipe making raping noise. Can't tell people sound travels. Where do I find the park & neutral switch. If the alternator burnt would it keep it from turning over. Will wait for response