Was running mountain lion 10.8.5 on my 2012 MacBook. Downloaded Yosemite, restarted, loading started and then it would give me a error message saying the disc needs to verify or repair or something like that. Go to disk utility, verify a problem and click repair. Says it has to stop repairing and I need to backup as many files as I can. I tried opening up osx utilities and reinstalling osx. But it won't let me because mountain lion I no longer available in App Store. And now whenever I turn on the computer it goes straight to osx utilities every time and gives me no option to try to install Yosemite. What do I do?