Murray Tractor does not move in gear?

Hello
I have a 405000X8B Murray Tractor. worked fine two days ago when I put in Garage. Today I started it and mysteriously does not move in gear. I put it on jacks and the wheels turn when in gear, but will not move with enough oomff with me on it... at all. Have adjusted the brake and cluch but to no avail. ANy suggestions and/or questions to help "you" would be greatly apprec iated... just stumped. DID NOT change drive belt yet ($$$).

Joe
June 2009