A .NET Passport uses your e-mail address to provide you with personalized access to Passport-enabled services and Web sites.
To remove the stored user names and passwords:-
Start>Run>Control Userpasswords2 >ok
Now Click the Advanced tab of User Accounts window.
Click Manage passwords tab under Advanced option.
Highlight the .NET entry you want to remove and click Remove tab.Close and Click Ok.
Remove the .NET entry.Click Close.