Has someone been harassing you via msn? If they're not interested in learning but rather have more nasty intentions then just block them. This way, they won't be able to contact you on msn. To block someone, right click on their name and you should see an option that says 'Block contact'. Click it and then a line should appear through their status. Now you won't be able to chat with them, and they won't be able to chat with you.
Apart from blocking them theres not really much else you can do. But there is an option on the newer versions of msn that allows you to 'block and report abuse'. I have windows live msn and to do so I just open a new chat window with the person I wish to block and you'll see an option in the top far right corner that says 'Block', click it and you'll see an option that says 'block and report abuse'. Select it and follow the instructions that appear on your screen.
In the future, be more careful and selective about who you share your msn details with, or you'll end up blocking many people.
Hope this has been helpful ^_^