I had my MacBook Pro 17", late 2011, in for a replacement of the motherboard. The technician in the Apple Store told me that their diagnostics said that not only my mainboard had failed, but also both my hard drives (SSD and HDD in SuperDrive slot). I asked them to NOT replace the hard drives. When I got the laptop back, I can boot up normally and all my data is still there and accessible. Should I nonetheless replace my hard drive? Is there any possible damage the hard drives could have that I can't see, despite them working from what I can see?