murray will not move?

I have a 1996 40" murray 40708x92a been sitting for a few years. got the mower started and running fine now when i put it in any gear makes a little noise like it wants to move but doesn't. the belt (37x61) is turning along with the engine pulley the tension pulley and the big pulley on the transaxel but nothing is happening. can you please guide me in what to do. thanks for any help.

Big E
March 2009