Sound not working on laptop computer

Question

hi, the sound on my computer isnt working. i have sigmatel sounds
driver and the sigmatel high definition audio codec is not working.
when i click update from sounds section of control panel, it says it
cannot find staco.dll i have a dell inspiron 6400 running windows xp.
please help me! p.s. it is not a notebook but this is the only inspiron i could find in product section. it is a normal laptop computer.