I have a 13 inch Macbook Pro, early 2011 with its original OS. I came to a point where its battery needs to be replaced, and I can't use it without using its charger/adapter. One time, I accidentally pulled out the charger and it turned off. It was not my first time so I just didn't worry. But when I plugged it back and turned on the laptop, it just got stuck at the gray screen with the Apple logo, the wheel, and a loading bar. At first I thought I should just wait, but later I realized it's still stuck for almost an hour!
I tried to Google and I read that something is corrupt.
I don't really have too important files, so it's okay if I would need to reinstall the OS. Or do I need to change the laptop's hard drive?