I know it's quite some time since this problem appeared, but I had the same trouble recently with the same model laptop. I was not able to find an answer on the internet, so I muddled along on my own.
I used ccleaner to remove all temporary files, then used the registry cleaner to remove all problems found when scanning. After the first scan was completed, I backed up the registry before removing the problems. A second and third scan showed more problems and they were cleared by ccleaner.
After a reboot, I ran another registry scan with ccleaner and it found and fixed those, as well as the problems found by a second scan.
I then removed the driver for the sound device in the system manager and rebooted.
The device was detected during the startup and the sound started to work again!
It's late for this fellow, but it might help someone else.