media buttons in front

I have an Inspiron E1505.  It has the buttons on the front of the  notebook that control volume, pause, fast forward, rewind, etc.  Before I replaced the hard drive, when I pushed the volume buttons, a pop-up appeared that showed the volume level.  After replacing the hard drive, the pop-up no longer appears.  Any ideas on how to get the pop-up back?

Thank you,