Volume buttons and mute/unmute buttons don't work

To assign any new function you would need a software for it. Is a lot better to just use functions already on system, like Fn+F8 (on my Acer). Is just a key more.

sharonannmoo,
Right click on the volume control icon located on bottom right taskbar. It looks like a speaker. Choose open volume mixer. You will then see where to mute/unmute the volume.
Thank You,
Dell-Jesse L
Dell Social Media and Communities

what Operating System are you running on the computer?

The touch sensors and "volume" button is on the top right corner of the keyboard panel .... above the keyboard keys. press "1" - left most - to mute and unmute press "2" - next - going right - to turn volume down press "3" - next - going right - to turn volume up
or ..
you can press (at the same time) the Fn key and Esc (to mute), Fn key and F1 to decrease the volume, or Fn key and F2 to increase the volume.

The keyboard's additional keys need driver software in order to operate properly. If you have the drivers at hand just install them. Otherwise look for a folder named SWSetup on your local drive, HP usually keeps the drivers in that folder, and install your drivers.
If you can't find both accessible go to this page and download your specific driver.
http://support.euro.dell.com/support/downloads/driverslist.aspx?c=ly&l=en&s=gen&ServiceTag=&SystemID=INS_PNT_P4M_8600&os=WW1&osl=en&catid=&impid=

Try to unmute from the taskbar control, see if it work. Also try reinstalling sound driver of the system

You need to reinstall the drivers. Get these from support.dell.com

The Dell has a "Fn" key. The "Fn" used with other keys control special features. I have a Dell keyboard here, on it holding the "Fn" and pressing "End" will alternately mute/unmute the speakers. "Fn" + "Page up" will raise volume, "Fn" + "Page down" will lower. You may have the volume muted, or turned all the way down.
The keyboard I have is from an 1100, your "Fn" key combinations may vary from mine.

Here's how I fixed mine with Win-VISTA:

1. Click START
2. Click CONTROL PANEL
3. (Switch to CLASSIC VIEW)
a. Click on SOUND
b. Click on PLAYBACK Tab
c. Click on SPEAKERS/HEADPHONES
d. Click on PROPERTIES
e. Click on CUSTOM Tab
i. Make sure PC SPK MUTE is NOT checked
f. Click on LEVELS Tab
i. Slide PC SPEAKER to 100%
ii. Don’t worry about the SPEAKER slider, it’s controlled by the keyboard buttons
g. Click on ENHANCEMENTS Tab
i. Make sure LOUDNESS EQUALIZATION is checked
h. Click OK
i. Click OK
4. Close CONTROL PANEL

If your volume controls are not working you may need to reinstall or update your drivers. These drivers are available via the dell website just use this link.
http://support.dell.com/support/downloads/index.aspx?c=us&l=en&s=gen