Ethernet cable not detected

One of my Windows 7 computer has been getting an error for 24 hours that the ethernet cable is not detected and it can not connect to the internet. Other Windows 7 computers on the same router/internet connection work fine.

I have already tried the following all of which were not successful.
-Plug in a different cable.
-Reboot the computer.
-Disable and then re-enable the connection.
-Restore to a previous system point.
-Inspect the connector for a problem with the pins.
-Look at the device manager for problems.
-Work through the windows troubleshooter.

The device is described as a Broadcom Netlink Gigabit Ethernet, although it does not appear to be a separate card and looks to be built into the motherboard. The Motherboard is Alienware 04VFW2 version A02.

Any help is appreciated.

Thanks.

Thanks for the help. Indeed I did try a known-good cable and a known-port. In addition to the above, I deleted the nic and drivers from the device manager and reinstall which was also not successful. It must be a failed onboard nic.

Its a desktop. Thanks keg, I did check the wires and they are not bent. Im planning on going out to buy and install a new nic card today.