Now that the price thing is out of the way, you should look for models that include the GeForce Go 5700 / Mobility Radeon 9700 or better, since those these games require some video card muscle. Battlefield and D3 Love lots of ram too, so you should look for 512 / 1 GB models. As for processor Athlon 64 is the best video gaming performer; avoid prescott based models because of heat / battery life issues.
The new mobility radeon 9800 has far more power than any other laptop video card so if you find an affordable model with it , you hould be able to play confortably D3 / BF1942.
Those are rough guidelines, there are other factors to consider. Is this a deesktop replacement system or is a system that won't be plugged and is dependant on battery life?
The Internet wrote:
"[The] 360 starts at the factory, moves to retail shelves, into consumer's homes, back to Microsoft. So THAT'S why Microsoft called it the 360...It all comes full-circle