Freshman bitches. 
Try downloading and running the standalone installer.
I’ve seen sound just stop working countless times from Vista SP1. Once we get SP1 installed properly, Windows update should find and pull the updated sound drivers compatible with SP1 for you, and you should be good to go. Try that, see if it works, and if it does, run auto updates again, and get everything you can. Let us know. That’s my best guess without actually taking a look at the machine.