How to Remove an Instant Messaging User Account from the List of Windows Messenger Users
To remove an instant messaging user account from the list of Windows Messenger users:
For users of stand-alone or workgroup computers:
1. Click Start, and then click Control Panel.
2. Click User Accounts.
3. Click your user account.
4. Under Related Tasks, click Manage my network passwords.
5. Click the user account that you want to remove in the Stored User Names and Passwords box, and then click Remove.
6. Click OK to confirm that you want to remove this user.
7. Click Close