It look like a lot of people have the same problem i had where after the windows update the sound card/audio driver stopped working.
For a quick fix do a system restore from the point of the update. This might be an obvious solution for some people but it's worked for me.
I've also changed my windows updates to be downloaded but need confirmation by me to be installed so if it tries to update again then i might be able to tell which update is messing things up and leave it out.