A hard reset will do it. The WEP key is a Wired Equivilant Privacy, basically and encrypted method for a wireless network card to talk to the router securely.
A hard reset will open up the channel so other wireless netwrok cards in your area will be able to connect to your router and internet access. So if you using cat 5 rather than wireless just disable the wireless interface or create a new wep key.
This can all be done from a browser on
http://192.168.1.1 usually.
Password and username may vary but usually admin password intially.
