The Garmin Nuvi 42LM is a navigational device: 5 inches wide, 3.1 inches tall, depth of 0.7 inches, and weighs only 5.27 ounces. It was announced on Garmin in 2013, but has been discontinued.
With power cable attached, try holding the power button for 10-20 seconds until the Garmin resets. Mine will fail to turn on or lock up sometimes and this reset procedure will bring it back.