I have a Dell Inspiron E1705 and there are audio/video controls on the front side of the computer. I can usually control the Volume settings using these buttons, but the screen with the volume no longer comes up. It still controls the volume, but the screen with the volume no longer appears; I can only hear the volume being increased and not SEE it actually getting higher.
I looked through the users manual for your computer on the Dell site and did not see any mention of a visual display of the volume setting when using the buttons on the front.
I have a Inspiron 6000 with the same buttons and have never had any kind of visual display when I use them. Are you sure you had this previously? If so, when did it stop working?
One possibility would be to try a System Restore to a time before it stopped working, see if that gets it back.
Other than that, if you look in Device Manager (Start / Run type devmgmt.msc and press Enter), do you see any yellow or red marks?
It was during the process of removing viruses/malware over this past week that the volume control stopped appearing on screen.
How to I go about turning it back on?