Go to Start/Search and type
devmgmt.msc, right click the
devmgmt results and
Run As Administrator. In the Elevated
Device Manager, are there any devices with Yellow Flags or Red X's. If so, a Red X means it is disabled, Right click it and
Enable it. If it is a Yellow Flag, then it needs drivers installed.
Go to the Dell Support/Download Drivers site, type in your Service Tag # or use this link
Product Support | Dell US and download the IDT Audio driver for your model.