Inspiron 15R Battery Life

I recently bought an Inspiron 15R laptop with the following configuration - i5-460, 4GB, 500GB, 1GB ATI 550v Graphics card. I am quite happy with the laptop except for the audio level, which is on the lower side, and the screen quality which looks a bit pixelated, however, I have learnt to live with it. But what really bugs me is the battery life. I always knew that the graphics card is going to eat up into some of the battery life but what I am currently getting seems like a serious performance issue. The Dell Inspiron product page claims a battery life of 4 hours and 2 minutes, however, what I get is approx. 2 hours of battery life and that is when on light usage ( web-surfing, music, videos)  without any gaming or CPU intensive jobs. It this normal? My laptop is just 2 weeks old, so with this kind of battery performance, I am quite skeptical about the life of this battery.  What should I do about this? Please advise.