Mandatory Messenger Update
Unless you are a Windows 2000 user, you will be required to update your version of Messenger
to fix a potential security flaw.
We will soon configure the service such that any user on Windows XP or later has to use Windows Live Messenger 8.1," Anand said. "When a user using an older version of Messenger tries to log in, the client will help the user with a mandatory upgrade to Messenger 8.1.