How do i fix this sound problem?

okay so ive had my computer for like 2 years. All of a sudden about a month ago i was trying to watch a movie on the internet and the sound wasnt working...then i realized it was all the sound on the internet... sidereel and all those free movies and shows websites, youtube, even the facebook notification and clicking sounds werent working. It hasnt been working still for the last month. Then i was on skype and noticed that that sound WAS WORKING so it cant be my speakers. skype still has sound so it doesnt make sense. Finally, a few days ago i put a dvd into my computer so i could watch it and i realized windows media player doesnt have sound either. So basically the only thing on my entire computer is my skype (game sounds dont work either)... so what do i do? is there any way to fix this problem without bring my computer in and paying? because obviously the speakers arent broken..any ideas? preferably from someone with experience with computers:)