Network Diagnostic Procedures

Uninstall and reinstall the network adapter.
a) Open Device Manager by clicking the Start button, clicking Control Panel, clicking System and Security, and then, under System, clicking Device Manager. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
b) In the list of hardware categories, find the Network adapter, and then double-click the device name.
c) Click the Driver tab, click Uninstall.
d) Click Ok.
e) Restart the computer.


Reinstall network card driver

Are you able to see any available wireless networks?

Make sure the wireless radio is on, the wireless switch should be located above the keyboard, it has the picture of a satellite.

Check that wireless service is running
XP: Click Start, click Run, type services.msc, then press Enter.
Scroll down to "Wireless Zero Configuration" and right click on it and select Properties. Set it to Automatic and not Disabled, and press the Start button, then click OK.
That should start the service.
7 (vista): Click Start, type services.msc, then press Enter.
Scroll down to "WLAN AutoConfig" and right click on it and select Properties. Set it to Automatic and not Disabled, and press the Start button, then click OK.
That should start the service.



To enable wireless adapter we need to go to device manager and enable it.
XP:
1. Right click on My Computer and click on properties.
2. Click on Hardware tab on system properties window.
3. Click on Device Manager
To go to device manager we need to click on the device manager button.
Now we can see all the hardware devices connected to the computer. To see the status of our wireless adapter click on network adapters.
4. Enable the Wireless adapter
To enable wireless adapter, right click on it and click on enable.
7 (vista):

1. Open the Start Menu by clicking the Start button. Click on Control Panel.
   
2. In the Control Panel, click on Network and Internet.
   
3. In the Network and Internet panel, click Network and Sharing Center.
   
4. In the Network and Sharing Center, click "Manage network connections" in the Tasks list on the left side of the window.
   
5. The Network Connections manager will open. Right-click the icon labeled Wireless Network Connection and click Enable on the menu displayed.

The last step checks if you have the wireless switch on or off. Locate the wireless button (in the middle, above the keyboard). Try to toggle it, see if is says anything.

Go to Control Panel - System - Hardware tab - Device Manager and check the network adapter is OK.
If there is a yellow ? against the LAN driver and the wireless card then the device drivers for these device have to be installed.
After installation then you will n\be able to connect a LAN cable from your computer to the wireless router and configure the wireless settings.

To secure your wireless network from unauthorized access,please click on this link and follow my instructions :-http://www.fixya.com/support/r3559128-wireless_router_security

I believe your question is how to uninstall and reinstall the nic.
Go to control panel->system->hardware->device manager
alternatively type devmgmt.msc in the run dialog box
click on the plus sign infront of network adaptors right click on the network card present click on uninstall. You will get a warning that you are about to uninstall this device from your system, select OK and once that device is gone restart the system go to the action tab on the top in device manager and select scan for hard ware changes the network card would be reinstalled automatically.