Recently my 2010 15" MacBook Pro has been running slower and slower until it eventually crashed. Whenever I would boot up my computer, there would just be a flashing folder with a question mark. At first I thought my hard drive corrupted, so I ordered a new hard drive. I also ordered the 54 bit driver kit in order to make the repairs and decided to replace my CD drive.
I looked up the replacement guide on the website and everything went great. A few of the screws on the top right of the computer were hard to take out, but everything went smoothly and the guide was very helpful. I replaced my optical drive and hard drive and then reformatted my hard drive from a backup I had. The next day, however, my computer wouldn't recognize the new backup. That's when I recognized that the problem was probably with the hard drive cable. I ordered a new one, followed the guide, put in my old hard drive, and everything was great.
If your mac hard drive seems to be corrupted, before spending a lot of money on a new one like I did, make sure the problem is with the hard drive or with the cable. I read that some people took it to the apple store and the staff there told them. My sign was the flashing folder icon with a question mark in the middle. Also, the 54 bit driver kit rocks.