I would hate for you to take some advice from someone on here and it not work out and you blow your warranty out of the water.
I just got a new Dell Inspiron 15R laptop. The power cord that came with the laptop is marked Dell 90W AC Adaptor, Input AC 100 - 240V - 1.5A, Output DC 19.5V - 4.62A. It has a grounded 3 prong wall plug.
I have another power cord from an old Dell laptop with the exact same ratings (marked 90W AC Adapter with identical input and output specs). The old cord has a 2 prong wall plug with both prongs the same size - so I assume the wall plug on the old cord is not polarized.
Can I use the old cord on the new computer? I don't know anything about electrical issues so I would appreciate any advice. Thanks