1994 Geo Prizm Vibration Lead to Non-moving vehicle

Aloha,
I just got this prizm and I don't know much about the car. However, it had a vibration and in time, it got worst. We changed the Exhaust Piping (thinking that was the problem). Then just a month later, while driving on the highway, the car suddenly stopped dead on the road, but it was still running. When I went to move it, it wouldn't move. Its almost like the brakes locked up. Any suggestions on what might be the problem and also, is this a common problem for these cars?
Thank you, Tina