How come my volume works on the laptop but when i go on itunes, it doesnt work?!?!?

i have a compaq laptop. for some reason the volume isnt working. like i clik the volume ion at the bottom right side corner and put it to 100 but i can barely hear bella's lullaby! please help me! i want to hear that song! how can i fix my volume? i check to make sure it wasnt on mute and it isnt but it still isnt working. i thought mayeb it was becuase the lullaby was too soft so i played a rock song.. it was sooo quiet i could barely hear it! it works on youtube and eveyrwhere else... the volume only doesnt work on itunes!!!! now that is a sign something is wrong- lol :) please help me out! thanks! :)