I have the MacBook Air and running OS X 10.72. The internal hard drive does not mount. I get a message that says partition may be damaged. When I try to use utility recovery the drive look gray and it says I cannot mount it. How can I fix this?

I have the MacBook Air and running OS X 10.72. The internal hard drive does not mount. I get a message that says partition may be damaged. When I try to use utility recovery the drive image on the left looks gray and it says I cannot mount it. How can I fix this? It was working perfectly fine until I shut it down for the first time in about 2 weeks. When I tried to boot it back up it prompts me to put in my password and afterward I get a circle with a line across it. It can no longer find the internal drive. It won't recognize the peripherals to restart in safe mode. The installer disk is an earlier version and it won't allow me to test the hardware. Can someone help. I may have shut it down inappropriately but I'm not sure. Can someone help?

Emilio