I have an Arduino UNO board model R3. When plugged into a computer, the RX and TX lights, as well as power indicator turn on, but the programming environment cannot recognize it, and as far as the computer is concerned, does not recognize that there is even a device plugged in. I am running Windows 8.1 Pro. When I try with another Arduino UNO model R3 Make Edition, it works as expected, with the L and power indicators illuminating and the programming environment identifying the board.
It is a genuine Arduino, but the other one is the Make version with a soldered SOC rather than a socketed processor like the normal ones.
Ah yes both types do exist.
Some times the LEDs flash a different colour to the real ones too..A nice touch I thought.