If you restored the router to factory settings then you should check any documentation that came with it for the default key. It is may also be that it is now unencrypted and you need to repair your network adapter on your machine.

To repair you adapter do the following:
*. Temporarily turn off your firewall for this process.
2. Go to Run
*. Type CMD and press enter
4. In the command prompt type: "ipconfig /release" (without quotes. put space between ipconfig and /)
5. Press enter
6. Type "ipconfig /renew" (without quotes. put space between ipconfig and /)
7. Turn your firewall back on and check you connection

If the above worked then it indicates that the router is unencrypted. Go into your router control panel and turn encryption back on and set a new password. Check your documentation for steps on how to do this or look up on google. Alternatively, you can open the command prompt back up and type "ipconfig" without the quotes. Find the address labeled "Default gateway" and type that number into your web browser's address bar. It should take you to the router control panel.

Hope this helps