Sisters laptop made a new named connection on my Netgear router how do I get rid of it?

Hi, I have wireless on my dads laptop and my ipod..when I did my sisters it asked for the router number which I supplied. my connection is not Netgear, but now (NAME PC CONNECTION) and I cannot get on it. I tried making the network no password and etc and now my sister laptop wont work! is there anyway to completely wipe it off and re do it?