Like Gary said, if the machine is under warranty then I would suggest just sending it back, while there is no warranty seal, if they do see any signs of tampering then they may deem your warranty as void, thereby charging you for any repairs which they may have to do.
If it were a dead battery, then the power should still go to the motherboard itself, at least that was the case with an old laptop I have which doesn't work while not on the AC. Do you have any charger which you can use? I doubt that is the issue but always worth ruling it out, otherwise the issue is probably with the motherboard which should be covered by your warranty.