I know it is not sth new but I HAVE SOUND PROBLEMS in my VGN-FW21M Vaio laptop!!
The first time it happened I restarted it and it worked, but this time this is not the case...
The link you were suggesting above doesn't work in my case as it is not applicable with my model..
I have checked all the sound devices and they are "supposed" to be working!
I am really desperate!!! please help!
Don't worry for that, I had the same problem as your and I found the solution.
Try to uninstall your current driver and install the last version of your driver. After uninstalling the driver and reboot it to automatically reinstall it, the audio still may not work. Amazingly though, sometimes after putting the system in hibernate mode and coming back, the audio worked.
If it doesn't work, go to noaudiooutput.com, they have many suggestions. I found my solution there.