if power adapter has to be connected for the laptop to be on even with a good battery means that is not a laptop anymore but a desktop which means you can't use it in a car, plane, or whatever. do as rgd1101 suggested if still under warranty as that salesman\woman don't know what they are talking about. my hp pavilion laptop & my msi netbook don't have to be connected to external power to work as they are mean to be portable with their own power compared to a desktop computer that needs external power to work.