Messenger services

I am getting a spam from ‘messenger services’ for a web site www.popupbuster.com. Has anyone else experienced this?

Yes and it is annoying. You can disable it by follow this instruction: http://www.itc.virginia.edu/desktop/docs/messagepopup/
or let this software do it for you: http://www.xpantispy.org http://www.xpantispy.org/news-e.php

Is this a virus? How did I get this in the first place? Please bear with my ignorance. I have not been finding much info on this on the internet. Thanks.

No, it is not malware. It is a Micrsoft Service andit is not really bad, but the problem is, that anybody is able to send you a message.