I also had no audio on my laptop's (d900t) HD Audio card (Realtek ALC880)
when I installed Vista Ultimate x86. Solved the problem by
replacing the HD Audio Bus driver with an older version (6.xxx with 5.xxx).
I have deleted \Windows\Inf\hdaudbus.inf and
\Windows\System32\Drivers\hdaudbus.sys. When Vista asked for the HD Audio
Bus drivers I pointed to the right directory. I used the files
from this package:
If you downloaded the package from the above link you should extract its
contents. Then you should extract the following file to:
MSHDQFE\Win2K_XP\us\kb835221.exe. This contains the folder (commonfiles)
where you must point to when Windows asks for the HDA Bus driver.
I had to take ownership of the \Windows\System32\Drivers folder to delete
After the driver downgrade I had installed Realtek HDA drivers for Vista
v1.60. Now the audio is fine and Realtek HD Audio Manager is
Finally: Vista found an "unknown modem device" but I have no drivers
installed to it. So it is not the modem that causes the problem.