|I found the following audio driver on Dell's website for that model: http://support.dell.com/support/dow...|
Is that the one you tried installing?
Open up Device Manager (Start > Run > type: devmgmt.msc) and identify items listed that are marked yellow or red. Also, report back items listed in the "Sound, video and game controllers" section.
Assuming Device Manager checks out clean and you installed the proper driver, you should also ensure the Windows Audio service is running. Go to Start > Run > type: services.msc and locate Windows Audio. Open that item up, Start the service, and ensure the startup type is set to Automatic.
Apologies if I don't respond to your reply immediately. I don't check this site daily, but you're welcome to PM me as a reminder.