My sound does not work when I use windows xp on my macbook. When I boot up in Mac Os X my sound works normal, so it is not a hardware problem. I have however noticed that when I use XP, a red light burns in the port where headphones are plugged into. This i most likely related to my problem because the light has burned since the sound stopped working. When I plug my headphones in the port above the one with the red light I can hear through it.