Alright

This is the old way that works better if your friend have an old machine...
(sorry if I spell something wrong, because my MSN is on different language)
Go to Tools -> Options
in Options select Messages
And there disable the emoctions/smiles
Now open a chat window with who you want to disconnect
Make an emoction like

and copy it (ctrl + c) and paste it (ctrl + v) until you cant do it anymore... Now select all of that again, copy it, so you can past only one time, send and spam it
Now that you did it spam those emoction
SPAM UNTIL THE PERSON DC
What will happen? Simple his/her msn will have a "heart atack"
But why mine wont?
Because your emoctions are disable
What can make he/she DC faster? He/she have a lot of windows open, have a slow machine, or something like that
You can also freeze that person ^^
I have a freezer so if you want me to post it...
Ok
GOOD LUCK AND HAVE FUN
Edit: Guys please, I beg you (lol), stop saying you think this dont work, try it first :S
You make me look bad

Edit2: And for you who dont belive me you can add me on MSN, so we can crash each other's MSN Clients!!
Sounds fun huh?