Is your hard drive connected via a USB connector? Some companies need to load driver software for the USB enclosed hard drive to connect to the computer. Some will reconize the hard drive right away. If that is the case try reloading the software again, If your not sure go to plan B

Plan B

If you feel confident enough and have a regular PC handy I would connect the Hard drive as a slave and see if the computer can see it. The reason I asked about a PC is they are much easier to get access to the Hard drive ribbon, ETC.

If the computer does see your hard drive then you are in good shape except for the lost files. If you wish to recover the lost files then you will need to get a disc utility to recover the files and it can be a tedious proceedure and will work only if you've not written any new info to the hard drive. If you feel your in over your head time to buy a few beers and have your comupter buddy come over and fix you up.

Jerry