You can go ahead and reset the router by pressing and holding the reset button for about a minute.Then unplug and replug power to the router.Once the lights are fine on the router check for the ip address in your hardwired computer as follows.
Start -- Run -- cmd(winxp/win 2000)/command(win 98.95,me)
On the black screen typein ipconfig which will give you the ip address.The ip address should be 192.168.0.x.If you get that ip then typein ping 192.168.0.1,you should get 4 replies.
Then open IE and on the address bar typein http://192.168.0.1
Username : admin
Password : password (by default).
Once you login on the left ypu can find an option called wireless setting under setup.you can find all the security info over there.