So I've only had my first MacBook Pro for a few months now so I'm fairly new to the computer. This morning after restarting my computer, it went to the startup Apple logo screen with a loading bar only to shut down suddenly. After doing some googling, I was told to enter recovery mode (cmd r) and reinstall the OS, also being told my data would stay intact. When trying to select my hard disk to install the OS, it said it was locked and so I was advised to partition the drive in Disk Utility so I did. After this, I was able to reinstall the OS on the hard disk. When the installation had finished, however, it was as if I had just bought the computer. I had to re-enter my settings, location settings, apple username, etc. and everything. EVERYTHING was gone. Maybe I just don't understand. Maybe it's still here or I need to log in differently or access the hard disk differently. I don't know. Like I said, I'm still fairly new to this operating system. Can someone help me out? I'm hoping I'm just reading into this wrong and this isn't as giant as a disaster as it now seems. Thank you everyone.