My Dell Studio XPS 435MT 920 i7, 6Gb, Vista 64BIT SP2 has motherboard Nvidea High Definition Audio 0-3 (total 4) Channels-Driver 1.3.12.0 in Device Manager and Realtec High Definition Audio x1-Driver 6.0.1.6602. All are indicating Working Properly. But my Vista system sounds and all audio movie/recording playback has suddenly vanished. I've tried to make sure all the software audio systems are not muted or turned off, disabled, all turned to max volume. The stereo/bass sytem works fine on another PC and that other working system also doesn't work on the Dell 435MT. This also happened some time ago and a system restore recovered it but now my restore has not worked (not old enough?). The only recent events are normal updates on system and drivers and a fault with an AcGenral.dll when an exe file is launched. The motherboard seems to work ok as tapping the microphone leads to sound out on the speakers. Your help and advice please. This is driving me nuts!