SCOM has what I feel is a major bug in that it will allow you to save items (monitors, rules, overrides, etc.) in the default MP. Doing this is bad for a lot of reasons, and not only does SCOM allow you to do this, but it is the default option as well. In my case it turned out that an occasional lack of attention allowed me to do this and then removing MP’s later becomes a huge pain in the rear. Anyway I found this good article on how to clean up the mess.