How to reinstall drivers?

Go to Control Panel > System > [Hardware] > Device Manager. You will see a list of categories and devices installed and connected to your computer.  If your card was not installed with correct driver Windows will display it as "Unknown Device" or "Communication Device" or "Ethernet Controller". You can identify incorrectly installed devices by Question Mark or Exclamation Point next to the device.

The Device Manager may be holding multiple copies of the drivers which might be preventing the drivers from being loaded properly. In order to address the problem, please do the following:

Step 1 If the computer has other network devices, please make sure that they are not bridged.

Step 2 Boot into safe mode (press F8 during bootup). Once in safe mode, access the Device Manager (right-click My Computer, left-click Properties, left-click on the Hardware tab, left-click on Device Manager). Expand the network adapters category and determine if there are multiple copies of the driver. If so, please uninstall them one by one until they are removed completely.

Step 3 Go to Control Panel, Add/Remove programs, and uninstall the driver related to your new network adapter (if present).

Step 4 Reboot the computer and Windows should detect the network card on bootup.

Step 5 Insert the installation disk with the drivers which came with the network adapter. Select the 'Search for the Driver Automatically' option. If Windows does not find the driver automatically, select the advanced option where you can specify the location of the driver manually. Browse to the folder on the installation disk where the driver is located.