Unfortunately it appears your HDD has failed. Now there may be a couple of ways we can recover... they are slim chances but chances none the less,here we go.....
OK Now IF the HDD fault,is the main Board on the HDD, what one can do is buy a NEW drive exactly the same as the old. Now swap over the Bad board for the New known good one... This may simply sort out your problem, and if it worked one could simply replace it back into the Camera. Unfortunately, it may be the INTERNAL electronics, that is actually faulty, there is no real way to tell but to replace the main board, in saying this too one must remember that the doing of this may destroy the NEW main board you replace, this is simply a chance one must take, to try to recover your data.
The second way, and you would need one of these anyway to perform the first attempt. Is to obtain a USB to HDD Dongle, now hook up with that to your PC, and IF it is picked up, well then you can recover data. If it is NOT picked up, then there are softwares on the 'net that maybe able to recover some of the data.
link below for Free data recovery software.
http://free-backup.info/data-recovery-software.htm
