Hi, Soujiroh,
I'm not that knowledgeable about laptops myself yet, but I do know of a few things you should consider:
1) Laptops with the high-end, really fast Pentium chips can get quite hot -- so hot that some people have to buy a laptop "cooler" to put between their lap and the computer. My guess is that a P4 at 2.8GHz like that Dell 5160 you mention might be a real scorcher (but that's just conjecture -- I don't know it for a fact).
2) You might look at Toshiba and Fujitsu laptops. They typically get very positive reviews, look really sharp, and have good reputations for reliability. You prolly won't find either at a price that'll match a Dell though, so if money's tight (it was when I was in college!), you might wanna go with the Dell. But if performance is more important to you, look at other brands. And if you can find a laptop with an AMD chip rather than a Pentium, it'll run cooler and actually be faster than a P4 on typical Microsoft Office and most Adobe apps (except for Photoshop). Looooonnnngggg explanation on that subject, so I'll skip it here. (I'll assume you won't be getting into overclocking nonsense with your laptop ....)
3) Screen size is one of the key things to consider with laptops. The bigger screen you can afford, the better (obviously). Same with battery life -- compare battery life specs thoroughly before you buy. 😉
Hope these few things help you a little. 🙂 I'll let those with more laptop experience provide you with the more in-depth stuff.
Ken