Cable modem ethernet problem

[adie]

I am trying to set up wireless router but can't get the Cable modem to work with an ethernet lead. My modem has been working with a usb cable so i thought it would be best to set up the ethernet connection before attempting to connect it to a router.
When i plug the ethernet lead in the led on the modem does not light up. I have used my ethernet connection to connect to other things with no real problem so happy its not the card.
When i run the ntl disk it comes up with the following error whilst installing the modem ethernet:

A faulty or non-functional adapter has been found. Please remove the following malfunctioning adapters before continuing with installation. If this is a USB NIC that has been removed, please physically plug it back in:

Realtek RTL8139 Family PCI Fast Ethernet NIC
Realtek RTL8139 Family PCI Fast Ethernet NIC
Click the 'Fix' button to correct this problem.



Error Code :23

I have tried disabling all this on device manager but still no joy.
Does anyone have any idea what to do ?