Windows Vista trouble with sound

hi
i have a problem with sound in my windows

i have installed realtek ac97 audio driver and the windows has recognized it
but i cant hear any sound from my speakers or headphone

in speaker setup when i set the configuration to 'STEREO' and click the L or R Icons no sound is played

but when i set the configuration to QUADRAPHONIC , again L and R doesnt work but RL and RR play sound

in none of these configurations my speakers or headphones play musics

can anyone solve my problem ?

im really confused