What model router is it? If you don't know 100% sure what it is, you can find the IP address of it by going to Start > Run > Type "cmd" (w/o the quotes) > then type in "ipconfig/all" (again, no quotes) > and then look for the Default Gateway. That will be the IP address of the router.

Some are 192.168.0.1, 192.168.10.1, or 192.168.1.1. < Those are the most popular ones.