I didn't have the latest version, but now I do.
I opened the Run box and I literally typed...
"C:\Archivos de programa\Windows Live\Messenger\msnmsgr.exe" /PlusEnabled=0
That's the path to Live Messenger in my case. I pressed enter.
The login window poped out. I activated my account. When it finished loging in, there they were: the MP icons, submenus, everything
Could it have to do with having everything installed in spanish: Windows, Live Messenger, Messenger Plus...?
Could it have to do with having Windows XP instead of Vista?
Maybe I don't have the proper version of Live Messenger for the command to work?
I'm lost, what do you think ?