No need to run the cd that came with it. Enter this ip address in your web browser. 192.168.1.1
I get mixed up between dlink and linksys but I belive the user name and password are both admin. If the spear work try admin and public. It will be one of those combinations.
Once your into the router, click on wireless and then security. You might have to turn on manual encryption if it's a newer linksys.
Hope that helps. If you still can't get passed the first screen reset your router by simply pushing the tip of a pen in the reset hole. Press firmly for up to 10 seconds while keeping a eye on the front of the router. Once the status light goes out release the pen and your passwords are back to default.