|If the bios will not recognize the hard drive, or if it does but the hard drive cannot "behave" normally, the only way you can recover data off of it is...|
- pay a lot of money to have a data recovery expert take a crack at it - in most cases you pay nothing for the service itself if they can't recovery anything - however they can almost always recover at least SOME of the data - there are experts on the web, sometimes locally in large places, and many hard drive manufacturers have a data recovery service, some of which have a flat rate - you pay no more than xxx. Obviously the same hard drive brand's service would have the best chance of recovering the data.
- or - try to do part of what a data recovery expert would do yourself
- if the drive still spins, replace the drive's board with another one that is compatible with the model
- if the drive does not spin, or if replacing the board did not help, remove the disks - platters - inside the drive and transfer them to another drive that the platters are compatible with. At the very least you will probably need some screwdrivers with oddball tips - e.g. torx or a type of security screw tip.
You will need to be very careful about cleanliness while installing the platters and before you place the cover back on the drive if you want to use the resulting drive for an extended amount of time afterward, but it will work long enough for you to get data off of the platters in any case.
Since most people have NO access to compatible hard drive boards that will work with their model, and hard drive manufacturers no longer offer them for sale, your best best is to buy an identical model number used (or new if it's a recent drive) working drive off the web - the board from that should work with your drive, and if you need to you could transfer the platters from your dead drive to the working drive.
That may still NOT be enough - you may need special programs as well to recover your data - but it's worth a shot.