Stopping Win from saving .NET Passports

From: .net passport question (question_at_discussions.microsoft.com)
Date: 06/29/04 

Date: Tue, 29 Jun 2004 10:56:02 -0700

Hello...here's my question. I teach highschool and have on occasion signed in to msn messenger on a school computer. Is there anyway of stopping Windows XP from automatically storing your .NET passport username. What I find after using msn messenger is that my email address, as well as many others, appear as choices as email addresses when clicking Sign In. I know how to delete the info but am curious if there is a way to stop Windows from saving the info in the first place. As you can imagine I don't really want students knowing my personal email address.