And please why not just post one reply pointing to
About Messenger Plus! for Windows Live Messenger (MSN 8) and leave it at that? It's what we got that post for afterall.
There is no need to uninstall 3.63 as this will not work on WLM anyway (won't do any harm)...but Plus!Live will be able to import settings from it, so if you have changed settings in that it's best not to uninstall.