Issues with ASUS P4S533-MX Mobo

Hi,

I am having problem with my PC audio output wherein the audio is not very
clear ie: has a lot of noise.

I installed the latest drivers (WDM_3665.zip ) from Asus site but
still the problem persists. I also tried uninstalling & reinstalling
windows media player and winamp but still the problem persists.

Does anybody know the reason or can suggest me some debugging tricks.

PS: It works fine for the first few minutes after every reboot but afterwards
the audio has lot of noise.

Config:
Mobo: ASUS P4S533-MX
Bios revision: 1060
CPU: Celeron 2Ghz, Socket478
Integrated Graphics: SIS 651
OS : Win2k, sp4

thanks.