That new version they speak of is not the WLM 2011 version.
You are suggested to update to the latest 2009 version instead.
So you don't need to update to WLM 2011.
You can still use WLM 2009 (even on Windows Vista/7).
To manually update, simply download the latest vesion on
http://windows.microsoft.com/en-US/messenger/home
On that page find the link which points to the 'XP' version (which is WLM 2009).
eg:
http://g.live.com/1rewlive3/en/wlsetup-web.exe