Hi All Wondered if anyone has any suggestions for my issue. I've got a early 2011 macbook pro. Came with a 320GB HDD, and I replaced the optical drive with a 1TB HDD. All fine, for ages. Then I go to switch on this morning, and I get the flashing folder/question mark symbol. After restarting to the recovery mode, I ran disk utility, and my main disk wasn't showing up. Secondary 1TB disk is fine. Panic. I removed the HDD and plugged it into a USB-SATA adapter and started up again, and against all odds, it booted up right away from my main HDD, now in a USB caddy. So I'm thinking it's either the SATA cable or controller. But cable looks fine, and controller would surely affect the second HDD too. Does anyone else have any possible explanations? Thanks!