Toyota Repair: Engine wont start, even after battery change, locking doors, battery change

Question
I own a 2000 Camry V6. It hasn't had any problems until recently, when the automatic locking doors wouldn't open via remote. I then opened the door with my key and tried starting it, but it was completely dead. No lights, no sounds, nothing. My friend tried to charge the battery directly but the battery wouldn't hold a charge. I then had a friend jump start the car and it worked, and I drove around for about 40 minutes before parking. For about a week afterward, I didn't have time to drive the car, so when I tried to start it again, I was not too surprised to discover that it had died once again. I tried once again to jump start it, and it did start, but at that point I decided to go buy a new battery (old battery, which was only 2.5 years old, was bought at Costco, and bought the new battery at Costco again). After putting the new battery in, the car started fine and I drove for about 40 minutes home. That was 2 days ago. Today, the car won't start once again. However, unlike the first time, the doors unlock via remote, all the lights turn on when I put the key in, but everything shuts off (and there is no sound) when I turn the key to try to start the car. I also noticed that the clock was reset (and resets every time I take out and put the key back in). The lights all turn off when I step on the brake. Any idea what might be wrong? I would really, really appreciate any help! Thank you so much in advance.

Answer
It sounds like it may have a bad alternator,jump start it again and while the engine is running disconnect the negative battery terminal, if the engine does not keep running the alternator is the problem, you can also drive it to an autozone or similar autoparts store they will usually test the alternator for you at no charge.