How much power in an automobile inverter do I need to power this laptop?

I have a 15", eMachines laptop that I tried with a 200W Vector inverter from Target. It kept overheating while trying to play a DVD while driving. On the laptop AC adapter, it says, "INPUT 2.0A, OUTPUT 6.3A." How big of an inverter should I go to to make sure I can plays DVDs while driving?
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