there are two fans, the auxilary and the primary. the primary is on the engine side of the radiator is is controlled by the fan clutch. with your car off reach in there and spin the fan, there should be some resistance. the fan on the other side of the radiator is the is the auxiliary radiator fan, if this is the one not running it could be a number of things... ie -> faulty thermostat, fusues, air trapped in radiator....
start with fuses, then thermostat, then report back and we'lll have a cup of coffee or something