I have a 17-inch, Mid 2009 MacBook Pro, running on OS X 10.8.3. This past christmas my dad took out my disk drive for me and installed a solid state, that I run my operating system off of. I kept my old hard drive and mostly use it to store files and such since it's bigger - important files. I was using it today to browse the internet and work on an Indesign document when it started making a weird beeping noise from inside the computer, not from the audio or the speakers (I tried turning the sound on and off, and increasing the volume but it made no difference, it also sounded like it was coming from about my "Command" key, rather than the speakers on either side). The sound is a little like a truck backing up, but softer, with each beep coming 2 seconds apart. After that it restarted and my hard drive was gone. I can still open the computer and run it off my solid state, but as far as the computer seems to be concerned there is no other hard drive installed. The beeping noise is ongoing. Can anyone tell me what happened, where my hard drive went, and how likely it is that all my files are gone or not (I do have backups, but it was from a couple weeks ago, and my Solid State is simply not big enough to hold everything, I really liked having both hard drives)? Also, what is with this weird beeping noise?