I must admit I am absolutely furious right now.
I downloaded the Vista SP1 update and now my pc is totally silent.
I have tried unistalling and reinstalling the soundcard drivers, updating them, rolling them back...ad infinitum - but the pc is silent.
My speakers are virtually new and they are not the problem (tested them).
Yes I have checked that the sound is not muted and gone through all the settings, and re-booted the pc after every change of setting.
It would appear that this is one of a number of 'bugs' in Vista SP1 that users are aware of - but there would also appear to be no resolution to the problem either.
I have a Realtek High Definition soundcard that came as the installed card a year ago. Realtek released a driver update in the last day or so and I have tried that too - with no joy.
Does anyone have any idea as to how I can resolve or workaround this?
Or......do I have to wait for Microsoft to pick up the gauntlet?

Any help with this would be much appreciated.
(I've even considered uninstalling Vista SP1 - but would that cause even more grief than I have now?)