CentOS - Dec 2008 - MCP51 sound card can be recognized but can't work

Hi all,
I recently install CentOS 5.2 on my Asus Z99M laptop, everything seem to
works fine but there is some problem with the sound card.
The system can recognized the hardware and I can even run the Realplayer for
linux without any error messages, but it can't make any sound, or even
noise.
I have googled a lot but still can't get it work.
Will anyone please guide me to solve this problem, step by step or just give
me some reference. I will provide any information needed.
Many thanks!
Cheers, Xiaobo
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.centos.org/pipermail/centos/attachments/20081223/d2f31c80/attachment-0003.html>

--- On Mon, 12/22/08, Xiaobo Zhu <xiaobo at zhu.net> wrote:
> From: Xiaobo Zhu <xiaobo at zhu.net>
> Subject: [CentOS] MCP51 sound card can be recognized but can't work
> To: centos at centos.org
> Date: Monday, December 22, 2008, 10:16 PM
> Hi all,
> I recently install CentOS 5.2 on my Asus Z99M laptop,
> everything seem to
> works fine but there is some problem with the sound card.
> The system can recognized the hardware and I can even run
> the Realplayer for
> linux without any error messages, but it can't make any
> sound, or even
> noise.
> I have googled a lot but still can't get it work.
Open the mixer window and check the sliders and switches. It should say
"hda nvidia" at the bottom.

The box I'm responding with has the nvidia MCP55 chipset. Should be similar 
to yours - I've never had a glitch.

-- 
Mark