When I try to sign in to my Linksys security screen there is another ID there too. How do I delete it?

I was told by Linksys that since this is a wired router, there is only one password and the other ID would have to know the password to get into my system.

So my question is, how do I eliminate this other entry in Windows XP? Linksys says you have to get rid of that in Windows XP!
I don’t have wifi! I am wired!