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Windows 7, Vista and XP can provide updates and drivers to currently installed or new adapters using Windows Update. As soon as the device is plugged in or recently installed, Windows will attempt to connect to the Internet and download the drivers automatically.
Use the following steps to let Windows do the installation for you.
Step 1: Use an Ethernet cable and plug your computer directly to your router. Make sure Internet is accessible.
Step 2: Place your new adapter in the proper slot or port.
Step 3: With your computer running, a bubble message will appear stating that this device was not installed successfully. Left click on the message.
Step 4: On driver installation failure, you can change the setting to use Windows Update by clicking Change setting...
Step 5: Chose to allow Windows to update your driver when it is not found on you computer.
Step 6: Once the driver installs successfully, close the window.
Step 7: Click/Right Click on the Network Icon located on the system tray to View the Available Wireless Networks. Find your personal Network and double click to connect. It should request for a wireless key, which by now should have been set up.
At this point, there should be a connection to your Network.

Driver Installation through the Device Manager
Step 1: In the Start menu, right-click on Computer to select Manage.
Step 2: On the left, select Device Manager to bring it up on the right.
Note: If the Driver software has not installed correctly, the partially installed adapter will come up in the Other devices group. Just as it is shown in the previous image.
Step 3: Right click on the unknown adapter to Update Driver Software..
Step 4: Click to Search automatically for updated driver software.
Note: If Windows was unable to install your Adapter, Windows may not be set to install automatically.
Step 5: Make sure the proper settings are selected by arriving to them with the followings routes:
Windows 7/Vista: Clink on Start > Right click Computer > Properties > Advanced system settings > Hardware tab > Device Installation Settings
Windows XP: Clink on Start > Right click My Computer > Properties > Hardware tab > Windows Update
Step 6: Click on Save Settings or OK to apply the change.
Confirmation of a successful Driver installation is achieved when the model of your adapter is label and listed in the Network adapters group of the Device Manager.