HDD now works from inside the laptop!

My Problem

My Macbook one day wouldn't boot, giving the folder/question mark story. The only way I could get a full boot was by making my internal drive an external. That narrowed the problem to either the HDD cable or the motherboard, I optimistically ordered the cable and started praying.

My Fix

The replacement took less than 5 minutes and afterward my broken computer was once became my trusty Macbook and booted without issue.

My Advice

If my repair has taught me anything: keep digging until you've narrowed it down as much as possible and then start with the cheapest fix.