Self Propelled Lawn Mower Wheels Won't Turn?
Most mowers are rear wheel drive, that means the power goes to the rear wheels. But some mowers like Craftsman are front, and some higher spec models are four wheel drive.
The first job, know which wheels do the driving. With that figured out, run the mower with drive engaged while the driving wheels are off the ground.
If the wheels turn, even slowly, it indicates that the drive system itself is likely OK. It may just need drive cable adjustment. I wrote a post on adjusting a drive cable here (Internal link).
If the wheels still don't move, we'll have to go deeper. With all wheels on the ground again and the the mower engine off.
Apply the drive lever, and pull the mower back ways. If the driven wheels (usually rear) lock up, it indicates that your drive cable is in place, however it could still need adjustment, so check out my adjusting a drive cable post here (internal link) or there is a problem with the drive belt.
To inspect the belt we'll need to disable the mower and turn it over.
If the rear wheels don't lock up, it likely indicates that the drive cable is out of adjustment, detached or broken. The mower will need to be disabled, turned over and the cable inspected.
To disable your mower, remove the plug wire and turn off the gas, if you have a gas tap. Always turn your mower over with the carburettor side facing up, this prevents gas flooding the air filter, engine and your work area.