About 2 days ago, I did a routine system check on my late 2008 unibody MacBook. Came back 100% clean, no OS corruption, no physical issues, nothing. But this morning, I went to get on, and Drive Genius told me I had potential OS corruption and to restart it to repair the issue. So, I did it. It couldn't fix the issue. The utility just said it couldn't, no explanation. I sat for a few hours trying to get different things to work. Not a single thing. So, I rebooted and just decided I would handle things as they came to me. No luck, as soon as the progress bar reached 100% it shut off. I retried several times, same result. I couldn't boot into safe mode either, it couldn't even find the is for that. I could boot into recovery, and I tried to do a disk repair there, but couldn't and it said it came back with a code 8. So I went back into drive genius. I went through the whole list of utilities. I decided to do a drive physical check. In 9 minutes it got to 0.6 percent with 4 damaged physical areas. It's now at 21% and 45 minutes with 9 damaged areas. What could have caused this? It was working before I went to bed with no errors, and as far as I know it hasn't been moved the entire night until I went to use it this morning.
Sounds like your drive just up and died all on its own and not because of anything you did. It happens.
Your hard drive was probably warranted by its manufacturer for 3 or 5 years so you got a good bit of extended use. I hope you're backed up...or that it doesn't matter. I have that exact model MB and the HD died a few months back. It's the easiest Mac laptop for swapping out the HD so go get an SSD and watch your MB come back to life. I also upgraded mine to 8GB RAM.