The first is the onboard audio and running on the default Windows driver
, which provides just enough functionality to get sound out of it. For the proper driver for it go here, Dell - Drivers and Downloads
use either the service tag number or look up the exact model of your Dell and get th driver there.
The second is the audio built into the video card (all four of them), so the card can send audio over HDMI when using the HDMI port and connected to an appropriate display.