Craftsman Riding Mower Won't Start

I have a Craftman riding mower. I was cutting and in the middle of that it just stopped. When I try to start it, it just makes a click noise. We tried to move it and the back wheels seem locked up and we can't push it. Does anyone have any idea what might be wrong? It's a newer model purchased in 07, but I don't have the model number with me.

By Mary