Most people use the home phone as the security code. Have you tried your own number? If not, then I would definitely go with a hard reset, which is on the router.
Have a look at the documentation which came with your router (or download the manual).
You connect computer to router with ethernet, log in to the user setup screens, go to wireless security, review or renew wireless security type and passphrase, apply them to wireless adapter's user interface (or Windows Wireless Connection), disconnect ethernet.
Most people use the home phone as the security code. Have you tried your own number? If not, then I would definitely go with a hard reset, which is on the router.