All sounds, both system and CD, suddenly not working

Could someone please help?

I have a Gateway 450x Series laptop system with SigmaTel
Codec Audio sound driver. Turned off my computer last
night, everything was fine, Windows closing sound played,
I went home.

Came in this morning, turned on my laptop, and there was
no sound, either system or regular audio CD's. The
speaker icon didn't even appear in the task bar.

Checked the control pannel and device manager. The
system detects the hardware but says, "This device cannot
start (Code 10).

I did a system restore and that didn't work. Re-
installed the driver for SigmaTel and that didn't work.
Called Gateway, they had me do the same, restored it back
further. Next step they said would be to do a Windows XP
repair attempt with the system CD to check for errors.
If this doesn't work, the want me to reload the entire
system and start from scratch. If that doesn't work,
then it goes in for service.

I'm hoping there's a better way to troubleshoot this
problem. It seems that the Gateway techs only know the
basics and have a tendancy to "push the bottom" using the
most extreme solution. Kind of like tearing down your
house and rebuilding it just to fix some siding that fell
off instead of just fixing the siding. Make sense?

Anyway, Gateway says that the problem is with Windows
XP. I'm not %100 convinced. I've had an XP system at
home for two years and have never seen, nor heard, of
sound just not working, suddenly stopping overnight. Can
anyone shed some light on this issue?

Thanks for any information you may have. Let me know if
you need anything else.