Installation and Removal : Stop MSN Messenger from automatically logging in when opened

Question: How can I prevent MSN Messenger from automatically signing in when I open it? Answer:

1. Click the Start Button, then Control Panel.
2. When there, choose User Accounts and select the account name you use want prevent from automatically signing in.
3. Look under Related Tasks on the left of the screen and select 'Manage my Network Passwords'. 4. In the new window, click the Passport.Net\* (Passport) entry and select 'Remove'.
5. Close Messenger and restart it.

Source ( there you have everything about MSN messenger)