I was using my MacBook today normally, and I started installing the OS X 12.5.7 update. It finished and it was supposed to restart, but I heard the mac booting sound, saw the apple logo and the twirling thing, and then it turned off. I turned it on again, and it did the same thing. I browsed some forums and tried doing CTRL+V thing, and the last thing it said was "CPU HALTED". What does that mean? Is this really bad for my computer? Did I lose my files? Please, any help would be greatly appreciated.