I've just dealt with the exact same issue.. all of the forums I've found online have suggested cycling the power and hitting f4 or f10 but to no avail. I had recently replaced my 1 terabyte hard drive with a solid state drive so I had the tools on hand to take my computer apart (just a t-5 torque driver and small phillips screw driver); I removed the bottom panel of my computer (Asus Q550LF) and started looking around; the hard drive was still firmly attached so I started looking at other connections on the board; Here's what my issue was, so maybe there's a small chance it will help you or someone else; I did drop my computer from table-height and that's what started all of this. I removed the battery (three small screws) and the other end of the strip that connects the hard drive to the mother board wasn't connected squarely. I could tell this because there are thin white horizontal lines the cross the strip to give a visual que to if the strip is in place. There's a small black (dark grey) bar that holds the strip on place. Using a pair of tweezers (admittedly not the right tool for the job - but they worked) I lifted the black bar and the strip came right out. I simply put the strip back into place, square with the connector and mother board, then pushed the black bar back down on top of it. Then, just screwed the battery back into place, put the cover back on, turned it over and it started right up. It might seem like a bit of a process, but better than replacing your computer or paying for unnecessary parts or service fees.. Good luck!