Most annoying tech support call ever:
Customer: Our computer won't boot. Come over and fix it.
Me: Please tell me what message you see on the screen which describes why the computer will not boot.
Customer: No, just come fix it.
Me: Okay, but we're charging for a service call even if I don't touch your computer.
Customer: Just fix it.
Me: (drive over, walk up to the office where the computer is at, pause at door and look in to read the screen across the room (younger me had much better vision) announce)
You have the mouse plugged into the keyboard port, and the keyboard plugged into the mouse port. Power the computer down and swap the connections and it will then boot.