I own an DELL Alienware M11x, it gives me a battery back up of around 5 hours with W8 64-bit.
However, today I connected it to an external monitor (Dell) while watching a movie and it gave me a battery back up of just about 2 hours.
At first, I thought it may be my antivirus which might be causing it, but I checked the last acitivities in my BitDefender and it didn't do anything during the time I was watching the movie. utorrent was continuously on and downloading a couple things via wifi but that is about it. The bluetooth was disabled and there were no other external devices conected at the time. Windows updates or scan(s) were not running either.
I just want to know if this is normal or if I should be worried to buy a new Battery(How about the DELL Alienware M11x batterij on the shop )