By default your routers ip should be 192.168.0.1. type this in the address bar of your web browser. this should bring up your routers page. Navigate your way to the security settings, You should have to login at this point.
User names and passwords can be found here.
http://artofhacking.com/etc/passwd-actiontec.htm
try all of those and see which one lets you in.
now youre in simply choose a type of password WEP etc and create the password (one you will remember). This password will be required when you logon to the network. Windows should then remember the password for you. If you do forget the password which you wont (remember!) you can go back to your routers page and reset everything or just the password. This will take off the password or change it to what you want.

Hope this helped
Bob.