I'm having the same trouble with registering as somebody else on this computer. Oh, by the way, I'm the husband of "violet".
When I try to register I get this message:
"Our records show that you have already registered at this board under the name of violet. If you have lost your password, click here. If you would like to modify your profile, click here."
So that foils the first option that was suggested. Then when I added myself as another Windows user on the computer, I still got the message above when I tried to register.