Its actually very easy to hide a weapon in a laptop even if you have to turn it on. You can just slip out the removable drive, and fill it with a gun or knife or bomb, then but a plastic cover over the removable drive to make it look normal. You can then switch it on and it will appear to be a normal computer. It really amazes me how easy it is to bypass any sort of security that they come up with. Even a young child can figure ways through the system.