my mini has been working fine since i got it, yet last night i shut it down like usual, and correctly to say the least. today after returning from school, i power up my mini and get to the login screen as i always have, i type my password and thats when it goes down hill. i get the screen with the apple symbol and the scrolling loading wheel thing.. about 30- 60 seconds later the apple symbol changes to a crossed out circle and stays loading until shutting down after some time. its a late 2012 mini so it doesn't have a cd drive. i heard its one of three issues... 1. hard drive failure. 2. software corrupting the hard drive. 3. or a bad shut down. can anyone explain to me how to run a diagnostics test, as any computer repair, or apple store would do to find out the issue. any information on how to fix any of these problems would greatly be appreciated.