An auto DC adapter has a cigarette lighter input plug on one end that is plugged into the cigarette lighter receptacle and on the other a special output connector that is plugged into the laptop's power receptacle. Although recent P4 laptops have higher and higher power requirements, auto batteries have the capacity to supply the necessary output for the PC.

TOSHIBA
    Toshiba AT100 Tablet PC,
    Toshiba AT100-001,
    Toshiba AT100-002,
    Toshiba AT100-004,
    Toshiba AT105-T1016,
    Toshiba AT105-T1016G,
    Toshiba AT105-T1032,
    Toshiba AT105-T1032G,
    Toshiba AT105-T108,
    Toshiba WT200-008,
    Toshiba WT200-00E

FUJITSU
    Fujitsu LifeBook MH330

NOKIA
    Nokia Booklet-1