If a hard disk drive is not recognised by the system BIOS, either the first time it is installed or after being in use, it might not be a dead drive, because the problem can be caused by a bug in the drive’s firmware.
For example, the Seagate Barracuda 7200.11 series of drives has a firmware bug that does just that. You can’t use Seagate’s or any other diagnostic tool because the BIOS has to recognise the drive before doing that is possible. The data is still on the drive, but it can’t be accessed. This particular firmware bug is discussed on this Wikipedia page: http://en.wikipedia.org/wiki/Seagate_Barracuda.
This problem can occur after installing a buggy firmware update. So, if you are locked out of your PC’s hard drive after having installed a firmware update, it is likely to be the cause.
Firmware – http://en.wikipedia.org/wiki/Firmware
Since the drive is not recognised by the system, you can’t apply the firmware update that fixes the problem. The drive has to be returned to the drive’s manufacturer to be repaired – free of charge if it is still under warranty, but charged for if not. The drive manufacturer can apply a firmware update without having to access the drive. However, you should note that it will be possible for the technical staff doing the restoration to access the data on the drive, which you might not want to happen if it contains information that you would not want anyone else to see.
It is because of cases like this one that you should always make regular restorable backups or system images of the drive should it fail. In a case like this one, you would just be able to buy a new drive, restore the backup/system image to it and destroy the old drive that contains the kind of data that you don’t want third-parties to access.
To find out if a particular make/model of drive has a known firmware bug, you have to find out what the drive’s make and model is and then visit the manufacturer’s website where information about any know problems will be provided. The make/model information will always be written on the drive itself.