[Neil]

The unit that plugs into the PC will not have a battery. Sometimes you have to press the button the the PC unit then press a button on the mouse and keyboard. They are often very small buttons that you press with the tip of a ball point pen. I have a logitech cordless mouse here and you press a little red button underneath it. Not sure if you press both buttons at once. The idea is that you tell both bits to talk to each other.