change of hdd did not work.
I went to the computer tech here at my college because by MacBook Pro turned off by itself and when I turned it back on, it gave me a blinking folder with question mark. They suggest that I should change the HDD. So I bought the HDD and have them replace it. They ran a test and it passed the test on the new one and the old one. So they don't know is. I would just like to know if you know what the problem is.
If the hard drives are good and it runs off the DVD, I would replace the hard drive cable. Check it's connectors first. Here's the cable: MacBook Pro 13" Unibody (Model A1278 Mid 2009/Mid 2010) Hard Drive Cable
Fix an unrecognized drive in your MacBook. Connects hard drive to logic board. Replacement SATA cable compatible with all Mid 2009 and Mid 2010 13" Unibody MacBook Pros. Options with or without bracket. — 17 available at 59.95 each.