Dell Alienware M11x R2 (Mid 2010) - Manual (Page 33)

CHAPTER 2: GETTING TO KNOW YOUR LAPTOP
33
F5 — Decrease Display Brightness
Press <Fn><F5> to decrease the brightness of the display.
F7 — Mute on/off
Press <Fn><F7> to enable or disable the mute function.
F8 — Decrease volume
Press <Fn><F8> to decrease the volume level.
F9 — Increase volume
Press <Fn><F9> to increase the volume level.
F10 — Rewind or Play previous track
Press <Fn><F10> to rewind or play previous track.
F11 — Play or Pause
Press <Fn><F11> to play or pause a track.
F12 — Fast Forward or Play next track
Press <Fn><F12> to fast forward or play the next track.