Audio Suddenly gone

   Not long after purchasing my Inspiron 1721 I received notice that there was a Vista update I needed to install.  The update, Service Pack 1, would not install, though I tried again and again.  When Windows 7 became available I decided to upgrade.  I learned I could not upgrade to W7 without SP1 installed.  After a month-long correspondence with a patient service tech at Microsoft, we were finally able to install SP1.  W7 installed with no problem after that.  However, somewhere in the process I lost audio.  When I place the cursor on the speaker icon it says "No Audio Output Device is installed."  I took this problem to the Microsoft tech and she (I am assuming gender from the name) said I needed to go either to the W7 specialist at Microsoft or to the manufacturer of my computer--Dell.  I have decided to do both.

   So, here I am.  I have, by the way, gone to "Device Manager," uninstalled drivers, and then looked for undated drivers.  I was told that my drivers are up-to-date.  To further taunt me, the computer has occasionally reported the sound device is working properly, while still saying no audio output device is installed.  I have plugged in headphones and still heard nothing.

   Suggestions short of buying a new laptop would be appreciated.