Well, you can always upgrade the laptop drive or get an external drive.
The laptop's battery backup makes it nice to have as a tank circuit. Can you get a dock for it? I was thinking of using a dock and wiring everything to it then just docking my laptop in the trunk when I wanted a computer in the car (Unfortuantely my tablet PC isn't powerful enough and my Dell can't use a dock.)
You can also power the laptop either with the power supply that comes with it and an inverter (cheapest solution) or getting the DC adapter for your laptop.
Now the laptop also includes it's own power management so you should be good to go with that as well.
I'd be worried about power of the computer it's self, but I'm not the one to ask, I'm putting a P4 3.0ghz in my car cuz I want to ensure that I have both a fast enough computer and a little bragging rights...