well, i have an hp dv5000 with the same audio device, and i got sound working no less than 5 minutes ago (therefore its not impossible...). i used the sp35558 driver (from 64bitdrivers.com:: Conexant AC'97 Audio Driver for Vista x64
) in an unusual way. i ran the exe file, and naturally it failed. then i went to control panel > all control panel items > device manager. right click on the sound card (under other devices) and choose update driver software > browse my computer for driver software > let me pick from a list of device drivers on my computer > sound, video and game controllers > have disk > browse > c:\swsetup\sp35558\cp6308Ba. there is the doomsday message about the unsigned driver breaking your computer, but i installed it anyway. it installed successfully, made some windows noises, then i got a message about how i wasnt supposed to install unsigned drivers, and how windows was going to stop all the new drivers
. so far they havent been stopped, because i still have sound. but, there is no telling what will happen after restart.
in vista, after every restart i had to hit F8 before windows booted and pick disable driver signature enforcement for my audio to work. i have a bad feeling i will have to do the same here...