Sound drivers do not work

I have a DV9720 (KC330UA), Vista laptop.  After 2 recoveries using the (1) the recovery partition; and (2) the recovery CDs my sound will not work.  I've tried to install drivers for it but it says 'No Audio Output device is present'.

I upgraded to Win7 (32bit) and I've experienced the same message.  Neither of the available drivers for Vista works.

It's like the hardware itself isn't being recognized.

Thanks

Dave