How do I get rid of a virus called sino gusto funny scandal ust pm nio...?

Each time I use yahoo messenger, I double click a friend to normally IM him/her. But before I am able to type a message, my mouse buzzes my friend, sends him/her this file, types this gibberish message in my availability, and relocates my cursor down alongside the left part of my screen for a few seconds until it allows me to control it again. Can Someone PLEASE tell me how to get rid of this virus/trojan/ or whatever this may be. Thank you in advance.