so your asking why you cannot use the Ethernet port on your motherboard even though you have tested the cable on another device, and changed drivers.
well it could be a driver issue, which would you please tell me what version of windows you are using ?
it could be a hardware issue as well, when you plug a cable from router/switch to the computer and look at the port on your PC, there should be 2 leds one n each side of the port, do we get any led's light up ? (and you tested this cable with another device and it worked plugged in the same switch ?)