I recently updated all my drivers from dell website - since it says that drivers need to be updated. Turns out that updating the bios driver was a big mistake. I was on ver9 and updated to latest, then sound card was not detected.
A temporary solution I found is to install the old version 9. But it works only for one restart. Next time I restart the system, the sound is gone. Install the bios version9, the sound is back. I dont know how long this charade will go on.
Does any one know a permanent solution to this.