A while back, I rigged one of my laptops to run off this converter that was basically made to power things that plugged into your cigarette lighter. I got it without a power supply and that's the thing that met the specs best.
Most all laptops run off DC(they have to with batteries ;P) so a direct connection to your cigarette lighter or even car battery would probably work. However, I have heard you can get voltage spikes and all, so there are regulators and such.
Do you have some converter and all for you're laptop or just a direct wire?
