Full of Desktop with banner of “thayet myo hacking day”

I have a serious problem with my Desktop computer that after downloading some file from the internet my PC shows some minor problem. I think this may be the problem of autorun or something like a virus but in April or May 1st when I opened my computer I couldn't see anything unless my desktop background and gradually a little banner displaying "that Myo hacking day" is starting to increase in number and at that time I couldn't control anything and my mouse cursor wasn't displayed. Can you suggest me about that?
