yamaha ac-xg audio device problem

i recently purchased a sony vaio pcg-grx570 laptop equipt with a yamaha audio
driver. When i updated to windows xp service pack 1 at microsoft.com, my yamaha driver
caused system instability. It gave me a message that it was not going to install
the driver because it could cause instability. I accidentally chose to install
driver anyway and now i have no sound. I subsequently investigated and found
out that this is a common problem
(http://eu.computers.toshiba-europe....p?FID=TRO000000
1b59)as well as in microsoft's knowlege base it detailed the same problem. So i
downloaded the new driver from the link i mentioned and unzipped it and now my
computer fails to recognize it. It goes through the installation process and
appears to recognize the yamaha audio but in the end it gives me the message
that it will not work and in my Hardware profile there is only the default
"Multimedia Audio Controller" in the Sound, video and game controllers tab, with
a yellow exclamation point. I triend to uninstall it and then scan for new
hardware and it just does the same thing over and over. I think I have to go
into REGEDIT I went to HKey local Machine, System, Current Control set, Class,
4d36e971 e325 etc ... to find the multimedia audio control device but i dont
know what to do when i get there? Can you help?
Steve @ sderose1@comcast.net or 9082561465 thank you

i forgot to mention that for some reason i have no system restore points
available and i did not archive my service pack 1 download so I don't know how
to uninstall the service pack 1 undate -what a mess