Download driver sound

...here is the windrivers forum link for your system:

http://forums.windrivers.com/showthread.php?t=83746

...and answer #6 is very useful for "what seems to be your main issue' here:

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Try this. Uninstall the audio driver (keep it on the comp but NOT installed).

Download and install this; http://support.microsoft.com/kb/888111/

Reboot and install the audio driver again and reboot.

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..an additional note here, please check on this site and see if they have a follow through or something similar:

http://support.microsoft.com/gp/other_audio_problems_windows

...and YES there are other software programs on the net to diagnose
all kinds of Windows issues, especially related to cards & drivers.

WW