Well if you think he's annoying why do you want to go out with him? This kind of reminds me of this guy last year that had a big crush on me but would never ask me out...and he was so annoying too! he would IM me all the time, going on and on about his life, which i thought was kind of selfish. Anyways, I finally asked him if he liked me and he said yes, we were going to go out, but I called it off cause I realized what a jerk he was.
This guy MAY just be annoying to try and impress you. That was the case in my situation.
Okay, I guess the point is, if you don't want him around, you should just block him on MSN and ignore him. Before that you could tell him how annoying he is, but if you aren't up to that I would just ignore him. It's really the best way.