Several times I have a display on my desktop screen listing software for free trial download, or to purchase. Each time, I cannot delete this display. I can drag it off the screen but when I try to log off, the "Strange Program" blocks the shutdown. If I go to the Apple icon & select shutdown I get: "do nothing and shutdown will occur in 51 sec. No luck, no shutdown. The only way to shutdown is to hold the off/on button down for several seconds. Any advice regarding these "Strange Programs" ?