Another option is to enable MAC Address filtering. Every network card or device has a unique MAC address associated with it, which can be added to a table of "safe" or "approved" addresses on your router via the Administration panel.
Only devices whose MAC address is in this list are able to access the router, Internet and so forth. This method is very secure and ideal if only a limited number of machines will be used on the network. However, if friends or family are likely to come round frequently with laptops and want access to the Internet, it can get a little tedious having to retrieve their MAC address and add it to the router.
To find your MAC address, either look on the network card (Also often found printed on the bottom of laptops on a sticker) or go Start - Run - CMD and press Enter. Type ipconfig /all and it will appear as "Physical Address".