Mother and sound card ASUS ALi Chipset A7A266

I had a similar problem and I just managed to solve it. I have a PC Chips motherboard and a creative sound blaster with 5.1 channels and it was all working fine. One day I noticed that only the sound that was only coming out of the left and right channels was actually being heard. Sound from the the rear and center/base speakers was not coming through. I thought the card was damaged so I bought another generic card which also supports 5.1 channels. This one was sounding from all channels but there was a lot of white noise coming along with any sound. I tried both sound cards on another computer and both worked perfectly there. I decided it must be a collision with another driver. It turned out to be the driver for the microphone that is built into the USB Logitec webcam. As soon as I disabled that driver the sound card started working properly. I hope this info helps others.

I hate to ask these questions, but have you dissabled the oboard sound (if any) in the bios as you could have a conflict. If you have done all the neccassary things, try going to Start>Run, then type 'dxdiag' and hit enter for Windows to do a sound driver diagnosis to help with your problem.