snd problem

[austin_mini75]

I recently installed half life 2 on my note book it works reallllllllllly good except for one thing. No sound from the charachter on any of the monitor. For example when you get of the train and there is the administrator talking I CANT HEAR IT. Could some pls help. My sys specs are:

Dell D505
1.6 centrino
512 RAM
Intel etrememe 855 series
Sigma Tel Audio

all latest drivers. As i said this is the only prob other then that smooth sailing all the way.