I have no prblem starting it up but in Forward gear and reverse gear it won't move. I have changed the drive belt because when it is in gear and running the drive belt spins ( and smokes a little ). Even when the mower is off and in neutral the back tires will not move, any suggestions?

Is the parking brake engaged? Common mistake not insulting intelligence. Maybe it is stuck and the handle broke of the actually piece

Hi,
Two common things happen. One is that the mower is shut off withou the pedal depressed; cure is top speed in neutral and let the pedal out to seat the belt. Don not think that is yours because of smoke. Is the variable speed pulley seized?
Peace,
Clarke