Removing login name & stopping undo’s

I am running Win98 workstations attached to an NT4 server.Using client for microsoft networks.

I would like to know if it is possible to stop win98 displaying the user name of the last person who was logged in, when the login box is displayed.Also if a user is logging in and changes there mind at the last minute and deletes their password after typing it someone else can come along and right click and undo. Is there anyway to disable this.