speaker functioning

hello friends,,,i have a 4+1 speaker set with my computer...it also has an in built FM player..if i play the FM player separately then it functions properly but if i attach it with the system it does not give audio...if i attach earphones separately with my computer then it functions....because of this i changed the connecting cable between the system and the speaker,,then also there was no improvement,,,,so now where is the problem???is it with the system? or with the speaker set??
So friends suggest me some measures that i can try it out in order to make my speaker function 😕 😕 😕