In their initial state, Microsoft Windows operating systems (98, ME, XP, 2000, NT) allow anyone on the internet to pop up Windows on your screen. There is no need for them to know anything about your computer and your computer does not care who does it.

Even less savory individuals may pop up messages on your screen that try to fool you into taking actions that may not be in your best interest.

The important thing to remember is that anyone, anywhere in the world can pop up one of these messages on your computer. At this time it looks as though all these messages will have "Messenger Service" in the Window title.

Also know that spam senders are using the Windows Message Service as another way to distribute their advertisements.