Chosen Solution
Hello there! My MBP stopped booting out of nowhere. I thought it might be the hard drive, and I wanted to change the internal HDD to SSD anyway, so I bought a new SSD and put it inside, but still no chance. I put the old HDD into a case and connected it to another mac: Seemed okay, I could read all my data and made another backup. I changed the drives again in order to format the old HDD and clean-install MacOS. Installation seemed to work for ~2h but then just stopped without any message (tried several times). Then I tried to boot from the new SSD externally, connected via USB. This worked, I installed El Capitan and I am still using it right now. The crazy thing is: While running on the external SSD I can read my data on the old HDD (internal), so it can’t be Logic Board nor SATA cable, can it? Any ideas what the problem might be & how to solve it? Thanks a lot in advance! Simon
Most likely your HD SATA cable is failing. You’ll likely need to replace it and its possible the drive will need a fresh format and OS install afterwards. But! Before you do this see if you have an Apple Store near you and pay them a visit (with the original Apple drive back in place). Apple has been replacing the drive cables for free for some. See if you can persuade them to do you as well. If they won’t do it, here’s the IFIXIT guide you’ll need to follow: MacBook Pro 13" Unibody Mid 2010 Hard Drive Cable Replacement
