No sound

Hello,
after installing my new motherboard i have found to have no sound at all. my speakers are switched on and they are plugged in tightly so that cant be my problem, i recieved a disc from the manufacturer of the motherboard as i have onboard realtek HD 1.71 sound. my PC says that no audio device conected, and yet i have mny headset and my speakers both plugged in, into different slots (front and back). i have tried to reinstalll the drivers but that doesnt work, i ve vchecked my BIOS setup to make sure that the ound card is active, and it is so im stuck and ive been tryin to figure it out all night.. please help