A super NT Authority?

My laptop has a virus that shuts down in 60 seconds by the name of NT Authority. I've looked around and everyone says to hit "Shutdown -a". I do so, but when i do, the countdown still continues and all the icons and toolbars disappear with only the background image and the countdown showing. when it does work however. the countdown may have stopped but for some reason it is still running, so it drains all of my CPU, thus, allowing me not to be able to do anything at all. Can't even virus scan, go into a doent, go on the internet. nothing. When can i do to resolve this?