what could be the problem with my sears craftsman riding mower?

my riding mower seems to be locked up and wont move. i think it is the rear end. i cant even roll it, even with it in neutral it is still locked up. i jacked the backend up off the ground and i can spin both wheels fine.when i take my brake off and try to move it like boggs down and my belt start smoking because it is spinning on the pulley off of the motor, but the pulley on the transaxel will not turn. what might be the problem?
it is a sears craftsman riding mower 16.5 hp 42""
model no. 917.271632

Tim
July 2005