Wireless routers are devices which allow an incoming Internet connection, such as that from a cable or DSL modem, to be split into a wireless signal which can be accessed by any computer in the immediate vicinity that has a wireless network adapter installed. Wireless networks can be much more convenient than cabled networks, since computers can be moved around while connected to the Internet, and it reduces the clutter of cables. The downside is that unwanted computers in your area may attempt to use your router to access the Internet. It is often possible to identify such squatters with your router's administrative information.
Open a web browser and connect to your router by typing in its URL. The basic URL set for many routers is either http://192.168.1.1/ or http://192.168.0.1/. The URL for your router should be its IP address. If you are unsure what yours is, do the following: click "Start," then "Run." Type "Command" and then press "OK." In the DOS pop-up, type "ipconfig," and then press "Enter." This will give you a list of information about your internet connection; the IP address listed under "Default Gateway" should be the IP address for your router.
Enter your router user name and password to log into your router. Entering the router's IP address into a browser will bring up a pop-up requesting this information.
Search through the administrative tools and menus that your router offers, for a list or table of DHCP clients or of attached, connected, or active devices or computers. Different routers have different administrative options, so menu labeling will vary, but there should be a place to find a list of devices and IP addresses currently using the network. For example, users of the popular Linksys WRT54GL router can click "Status," then on the "Local Network" sub menu, and finally click on "DHCP Clients table" to bring up a list of attached devices.