A few weeks ago, I brought an IPhone, new in box, from SIN for a friend in the US. I had no problems in SIN, in MOW, where I took a break in my journey, but in order to transfer to a domestic connecting flight, I had to spend fifteen minutes negotiating with the TSO's over the utility of opening up a brand new, sealed package containing an iphone so that they could watch me power it up and then down. They eventually decided that simply swabbing the package would be adequate. So, OP, if you run into a hard headed TSO that wants to open the laptop package, I would emphasize that it is a christmas present, is sealed, and proactively request that they pass it through the XRay machine on it's own and then swab it down in lieu of opening it up.