96 Cavalier won't start/stalls when boosted

[xcooneyx]

Just wondering if anyone could help with my problem!

About a week and a half ago was driving home and noticed my dash lights and headlights were dimming. Next day went to go out and my car wouldn't start. Wouldn't even turn over, had absolutely no power. Got a boost and it started up fine but when I put it in reverse it died. Tried this a second time, made sure everything was off and as soon as I took it out of park it died again. I decided to try running the car and disconnecting the positive from the battery and it died which I surely thought then that it was the alternator and was told by others that this was the case. So I went and bought an alternator, replaced it but the car is still doing the same thing. Any ideas as to what could be the problem would sure be appreciated.

96 Cav 2.2L 2dr cpe automatic