I have a Mac Mini that is a couple years old. It won't download anything including updates or iTunes songs. The icons on the desktop and in the folders are messed up, wrong, or missing. It will not log out, shut down, restart, or do anything under the apple menu. Some web pages are messed up/unreadable and sometimes I can't view videos and other things on the web. And I'm sure there are more problems I forgot or haven't found out about yet. I am not sure what I should do to fix all of these issues.