how to stop the drive belt from comming off the pulley?

I have the same mower with the same problem. There is nothing listed in the manual for the drive belt adjustment. The manual does list an adjustment for the brake......which is a part of the clutch. I have the mower deck off of my mower now, have been under it today looking for a way to make an adjustment. When the clutch pedal is depressed the drive belt is very slack......hence it jumps off the pulley. As an interium measure I have removed the back plate with the hole for towing a trailer that allows me access to the pulley for putting the belt back on. I am thinking either I add another idler pulley or remove a coil from the clutch spring. I bet there will never be another Craftsman mower in my garage.............

Woody Pake
October 2008