That does not look good. Where is says "Media," it should have a description of the hard drive (such as size and model number) and under the drive should be the volume (usually called +Macintosh HD+ ).
The usual first steps would be to reset PRAM
http://support.apple.com/kb/HT1379
and if that does not help, reset SMC
http://support.apple.com/kb/HT1543
which is basically unplugging ALL cables and power, and reconnecting using a precise procedure. When you reconnect the power cord, if you have been using an crowded or old power strip (surge suppressor), connect it directly to a wall power outlet, at least initially. Power it up with nothing connected, except for the power cord. Hopefully, it will start up from the internal drive again.
If it does not, connect just your keyboard/mouse, insert your Mac OS X installation disc (for the current system release) and restart with the C key held down. This forces startup from the optical drive and takes you to the Installer screen. Go up to the menu bar and under
Utilities, select to run Disk Utility. See if the internal drive appears in the sidebar, hopefully with more than just "Media." But if you get that same thing as before, select it and run a +Repair Disk+ on the +First Aid+ tab, if possible.
