When you configure Windows Messenger and MSN Messenger to automatically sign you in to the Microsoft .NET Messenger Service by using different Microsoft .NET Passport accounts, you are signed in to both Microsoft Messenger Service clients through the same .NET Passport account.
For example, if you are automatically signed in to Windows Messenger through one .NET Passport account, and you sign in to MSN Messenger through a different .NET Passport account, and then you click Sign me in automatically in the .NET Messenger Service window, you are signed in to Window Messenger through the same .NET Passport account that you used for MSN Messenger.
For example, if you are automatically signed in to Windows Messenger through one .NET Passport account, and you sign in to MSN Messenger through a different .NET Passport account, and then you click Sign me in automatically in the .NET Messenger Service window, you are signed in to Window Messenger through the same .NET Passport account that you used for MSN Messenger.