If you feel that its a hardware issue most probably some drivers were messed around (either added or updated) via windows update in the background.
Try this as a last resort (as i cant think of better options right now)
- Disable windows update for sometime
- download slim drivers : http://www.driverupdate.net/downloads/SlimDrivers-setup.exe
- let it download the db and scan ur system.
- if it shows something related to audio (infact others like chipser related, mei etc) update them one by one.
- keep a check on the driver details tab in device manager to make sure the update was indeed applied.
- restart pc if reqd.
- check your audio output.
- if it works just make sure to do a manual windows update scan and see the culprit and add it into the ignore list