I need help, i got a msn spam

Hello,
i need help fast. A few nights ago my friend on msn sent me a spam that says something like this, hey is this YOU?! on (a website).And i thought it was just a normal message so i clicked on it and ever since i clicked on it, my msn sends it to all of my friends with out me knowing. Also when im talking to my friends on msn the box where we chat closes and then i cant talk to them and its really pi****g me off i need help :(