Acer netbook Windows boot missing or boot failed

I was searching on the net and then my netbook froze so I hard pressed the power button to reset. And then all of a sudden it didn't boot up to the menu like it normally does. It says Default device boot missing or boot failed.my hard drive is not detected also.Im really worried because what really is important are my files pictures and documents. I did not have a back up for those things cause I thought things like these would never happen. How can I fix my computer and will my files be ever saved? please someone. thanks..