HOw do I change the user ID for a user that has been registered.

Registered where?

HOw do I change the user ID for a user that has been registered before in lotus. LOTUS

Am using lotus 7 on vista. There was a problem with the server. A new server was installed but a client is still recognizing the old user name and not the new user name on the new server. Can anyone help?

Lotus what? Lotus has several products. If you are talking about Lotus Notes, The current user is identified by an ID file that is installed locally. The Domino admin creates these ID files when they create a Notes user on the server.