HEADPHONES NOT WORKING :(

I have a HP Pavilion 10 TouchSmart 10-e004au Notebook PC. Whenever i plug in my headphones the sound comes out from the speakers instead of the headphones. my computer does not even respond when i plug in the headphones. i have tried with many differen headphones and it still doesnt work. i am not sure if there is something wrong with my computer or i need to download a software to make the sound work. i have had this problem ever since i have bought my laptop. PLEASE HELP