How do you stop Norton from putting irritating messages with appear and disappear anytime they like on your computer?

You can either send a nasty letter to Norton (which won't get you anywhere :/), or you can install other antivirus software (after, of course, uninstalling Norton). If you chose to install different antivirus software, I would recommend Microsoft Security Essentials which in my opinion is the best antivirus software out there. It is completely free. It doesn't slow down your system, or anything like other antivirus software do. I barely notice that I have it except when every once in a while it asks me to scan my computer (which is a good thing). If you don't want to download that, there is also AVG Free. It isn't nearly as good, it has advertisements, and it slows down your computer, but I like it way better than Norton.

Hopefully this helps, sorry that I don't know a way to stop Norton from doing that.