Serial number doesn't bring anything up...
but i would check that the drive belt is still on the pulleys and isn't laying slack... drive belt should be located above the deck just below the frame. try putting it in NEUTRAL, and then press the pedal down, be sure the belt tightens up...
Okay, according to the parts list it has a hydrostatic transmission.. could be an issue with it, but i would check that the belt hasn't fallen off any of the pulleys, engine pulley, idler pulleys then the trans pulley.