Check the transmission belt and the ground drive belt for wear or damage. Check for broken springs or linkages in the drive system. You can view the parts for Craftsman LT1500 model 247.288820 here: searspartsdirect.com/model/1at38387n9-000247/craftsman-247288820-front-engine-lawn-tractor-parts
. Replace any worn or broken parts and you may be able to get the riding mower going again. If you need more help, reply with more details and the full model number of your Craftsman LT1500 riding mower. You'll typically find the model number under the seat.