Once the NIC (Network Interface Card) is installed, verify the device driver for the NIC is loading and working properly. In MS Windows, this is done by opening the device manager and double clicking the Network Adapter label.
Find the actual Network Interface Card in the list and double click it. Under the General tab, in the Device Status window, the text should read "The device is working properly". If it is not working correctly, the device driver will likely need to be reinstalled.
Check LED indicators, on the NIC first if available, and then on the switch the NIC is connected to. LED indicators should be lit and green at both connections in most cases. If not, replace the cable connecting the NIC to the switch or networking device. If the LED indicators are green, often they will be flashing off and on in an uneven fashion. This is an indication that the Network Interface Card is connected and passing traffic correctly.