Dell Alienware M17x R2 (Early 2010) - Manual (Page 9)

9 CHAPTER 1: SETTING UP YOUR LAPTOP
Press the Power Button Connect the AC Adapter
WARNING: The AC adapter works with electrical outlets worldwide.
However, power connectors and power strips vary among countries.
Using an incompatible cable or improperly connecting the cable to a
power strip or electrical outlet may cause fire or equipment damage.
NOTE: The AC adapter should be connected to the laptop for maximum
gaming performance.