Within a couple of seconds [literally] of going online for the first time with my brand new XP I had these strange message boxes.
I am told that they are designed to be used by network administrators to give messages out to users, but they can be used when you are on the internet to send these spam things; ironically, all of mine were advertising software to stop the very same pop-up spam things!
However, it is very easy to disable the messages as described above.
I am still puzzled as to who sends them and how they actually arrive down my phone line though!
Sorry bit of a delayed reply, (been busy revising for physics and electronics exams). I've not looked but I've seen it mentioned here before. Do you know if it's downloaded and unzipped or it if's created on the pc as a log or somthing?
powertool - All they need to do is find a user running XP with the right software and that's enough. The messenger is so that people can contact each other over a network. The internet is one big network so they can contact you via over that. The info comes down your phone line in the same way web pages do. I'm not onto XP (yet), but you may even notice a decrease in the speed of webpages loading just before you get a pop-up, which is due to the extra information being downloaded.