|Please tell us a little more about your computer. It sounds like either the hard drive has failed, or the hard drive has come loose from the motherboard. It is also possible that it is a problem with the motherboard itself.|
I am assuming you are running the Hard Drive Test from BIOS. Have you tried placing the hard drive in a different SATA port on the motherboard? It could be that just the SATA it is currently connected to has failed. You could also place the hard drive in another computer and seeing if it gets recognized then, indicating it was a problem with the motherboard (in which case that computer is pretty much screwed. Contact your manufacturer to see if it's under warranty and if they'll replace it).
If neither of these work then most likely the hard drive is shot. You'll pretty much have to either get the hard drive replaced by the manufacturer or buy a new one.
One last thing, have you tried running system recovery off of the Vista Installation Discs?