How do i get my speakers to work?

alright my speakers are fine i kno that because i plugged them in to my mp3 and they worked fine but on my comp nothing happens. When i get up to a certain volume it crackles a bit but thats it. I checked the audio ting on the control panel but it said no audio device. I read something about reinstalling sound drivers or something but im not sure how to do that plz help thank you.