here is my situation: Me and my girlfriend just purchased a townhouse, the office is upstairs so i bought a Macbook pro which i can use downstairs while watching tv or in the bedroom.... I bought my girlfriend a macbook for the same purpose.. I plan on buying a dell ultrasharp 24" monitor and keep it in the office that way either one of us can go and plug our laptops in and use it at the desk. I want to keep a power supply up there for both of us to use, can i buy a spare 85w power supply and will it be safe for her macbook? since it comes with a 60W I know i can just buy a display from apple with the power supply and i'd love to but with all my expenses right now i cant justify paying an extra $500 Apple premium.