Unknown boot error...HELP

[jhawkaudi]

When my Macbook boots, I get a folder icon with a question mark in the middle. What does it mean?? What can i do to fix it??

 

[MacDawg]

Here is the support article

It isn't finding the operating system

 

[djtman]

I tried all of the things in the list

nothing works - the only thing that comes close is restarting and pressing the option (alt) key with the osx install disc. It finds it, but when I click it, the screen turns grey and stays that way.
Any suggestions?
-Terry😕