On a wireless network, the WPA key is a passphrase that protects the network from outside intruders. If a wireless router is set up with WPA encryption, you need the WPA key for network access and to make changes network settings. Gaming devices that allow you to play games online also generally require you to know the WPA key if you plan to connect them to the Internet wirelessly. In addition, to restore Internet access after reinstalling Windows, you need the WPA key if you plan to connect over Wi-Fi.
Reset the router if you can't log in or remember your router's username and password. Stick a pin or a paper clip into the reset button -- the small hole in the back or bottom of your router -- and keep this button pressed for about 15 seconds. The default factory settings should be in place after the router resets. Find the default username and password and log in.