Toshiba fan making annoying noise?

My Toshiba laptop fan is mmaking this horrible buzzing noise and is vibrating. my computer keeps saying that there is a problem with the cooling system. but the temperature is constantly around 38-45 degrees which is fine. the noise only happens when the fan is spinning. the computer shop wants to charge me $295 to fix it, but it isnt even a problem. its just this horrible sound. how can i stop it??