ac97

i´ve got a epox 8rda3+ motherboard with a ac97 soundcard onboard and, from a while ago it started to play some sounds only on the front speakers.I´ve bought a sb audigy ls recently but it still has the same problem.When i do the speakers test, they all play fine but when earing music or playing games, either the rear speakers don´t play or they play very low.I even reinstalled winxp again and i´ve done all the updates but the problem remains. When i turn the cmss on the audigy settings on the rear speakers play a little louder, but not at the same level as the front ones.I´ve tried all the settings i could think of,but none of them worked.If someone as any ideias or if something similar happened to anyone, i appreciate the help