If i were you I wouldnt even consider a mac. They are extremely nice, and Call of Duty on my friends 17in display looked absolutely amazing, the downside, $2500. They do run Windows XP now, if you could call it that. Dualbooting screws up alll sorts of things so i really wouldnt reccomend it. Windows is still better for school in my oppinion, unless you are going into video production or graphic design.
If i were looking in your pricerange, i would probably go with this one:Acer AS5672WLMi-ATI
its a bit large at 6.6lbs, but for a 15.4in display its pretty good. Nice harddrive and ram, webcam, and ATI Mobility Radeon X1600. The battery life is kind of on the short side, but you can always but a new one. I have one very similar to this and i love it. My only complaint is that it seems a bit flimsy, but its still an awesome deal.