RE: Inspiron 17R Headphones not recognized
Welcome to the Dell Community Forum,
Please try connecting any other head phones / external speaker in order to check the functionality.
You might also try un-installing the audio driver from Device manager and re-install the same from our support site here http://dell.to/1hcxG98 . Type in the Service Tag, click on Drivers and select the OS type in order to install the audio driver.