7.1 Problem in vista

Im running windows visat ultimate and having some problems with my 7.1 surround sound. Im using the on-board sound card on my Asus A8N-SLI nForce 4 SLI motherboard (not deluxe or premium just the regular one). I downloaded drivers from realtek and installed them but only the 2 front speakers and the sub work and the rest play sound but the sound is all messed up and it cracks. I dont think it is my speakers because I also have windows xp on the same computer and it works perfectly. I think that it is the drivers from realtek that are not worlking well with vista. Is there any beta drivers or a work around with this that someone knows? If so please help me on this. Thank you.