Hello I have the same issue with Realtec drivers and Vista.   After the audio stop working the first time, I had to restore the system back to the orginal software.  However, this time I started using system restore and created a restore point before
running any updates.   The audio worked until I installed vista service pack 2 then audio stop working.   It would look like this was the cause of the problem. 

   So  I then attempted to update the realtec drivers before installing service pack 2 , the audio stop working and I had to restore the system to get them working again.

   Where is the problem.    Something with the way the os reinstalls the drivers? 
 
   This leads to the real question,     Is there a way to store a restore point on a cd or other location.  I want to insure I can get back to a working condition while I try differant solutions to this issue

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