Hard Drive Not Found, Flashing Question Mark Appears

I've tried all the "fixes" to this problem, but none of them seem to work.

•When I hold option, no hard drives show up.

•When using Disk Utility from the install disk, no hard drives are found. (Shows up just as "Media.")

-If I wait long enough, they do show up, but problem still persists after repairs.

•Still doesn't boot after resetting PRAM

•I can't reinstall Mac OS because my computer does not recognize that there's a disk to install it on.

What makes this all weirder is that if I wait long enough, it seems to work just fine, but then once I shut it down, it won't restart any time soon.

I also seem to have a problem taking it out of sleep. The screen comes back on, but the spinning wheel shows up if I try to do anything before my fans spin up.