|If you were boot up with Linux CD (Ubuntu or Puppy Linux are two that come to mind) that might narrow possible suspects... If you can boot from a Linux DVD then you ought to be able to access the hard drive - as a resource to the Linux OS installed into RAM only. If you can boot via Linux but not locate/access the hard drive then it does tend to put the hard drive in the centre of the frame?|
Booting (successfully) with a Linux disk effectively checks out the basic system as likely OK - apart from the hard drive.
Ubuntu.com is where to download an ISO; save and burn to DVD; boot with that DVD.
You "may" need to access bios settings to change first boot device to CD/DVD as it may not be set that way at present? As soon as the system starts to boot - POST - there will be a message saying what key(s) to press to access bios.