Laptop Computers

Looking at getting one for work, what should I be looking for in a laptop? I'm looking at the lower scale of the market (under 2K), are their any brands I should stay away from, a brand I should buy, which processor is highly recommended etc. I guess dual layer DVD burner is pretty standard these days, as is 40/60/80 Gig HD etc. Or alternately, if I was looking on e-bay s/hand, what should I be wary of? As I drive around for work, I'm in my car 60% of the day, will heat be a factor (I do have air-con) & battery life/power source, can they be powered of cigarette lighters? I realise a d/side of laptops is they can't be up-graded. Then again, someone suggested that a palm pilot may do what I want anyway. If a palm pilot runs MS Excel, is an electronic diary, they could be on the money. Thoughts?