i solved this problem partially by installing the following driver on Windows Vista Ultimate (notebook built-in speakers does not work, only headphone output):
http://ftp.us.dell.com/audio/R157052.EXE
The audio specification is:
SIGMATEL STAC 92XX C-Major HD Audio, Driver, Windows Vista 32-bit, Windows Vista 64-bit, Multi Language, Multi System, v.6.10.0.5511, A04