Questioning Folder of Doom Fixed With New Cable
I was having more and more hard drive problems until finally I couldn't boot. I bought a new SSD (which I was planning to do anyway), but reinstalling OSX over Wifi kept failing at the reboot. After many hours searching online, I finally found someone with the same problem as me here on iFixit.
It was a pretty easy fix. Just make sure you don't shock the new parts. I would advise buying a new bracket, as it's only $10, and re-inserting the new cable into the old bracket is easy to screw up.
If you try to restore your Macbook over Wifi and get the Questioning Folder of Doom, this is probably the part you need. It's not just a bad drive. Make sure to run the full motherboard diagnostic first (boot while holding D or Option-D). It will take a long time and appear to not be doing anything, but trust me, it's running. If your motherboard is okay, all you need to do is get this cable. It's a cheap fix. Also make sure to have the right set of screwdrivers.