RE: Audio no longer working. NVIDIA Card can't be detected
After checking or installing latest BIOS version:
Note: Please create a restore point before attempting the next steps: Type Create A Restore Point onto search box and select Create
In device manager, expand Sound, Video and Game controller and expand it. Right click Intel Display Audio, and select Uninstall. In the Uninstall window, check the box Delete the driver software for this device.. Click OK to confirm and proceed with uninstallation. Please run or install the file (Realtek High Definition Audio Driver ) or download / run from your Dell product Support page.