Assuming you have data on there you would like to get off: If you have access to a linux machine or can run a linux boot disk, see if your computer can recognize it in that environment. If it can, which I'm guessing it will, try to run some recovery software on it. If none of that works then you may have a more advanced issue dealing with the controller chip. You can google for reliable and effective boot disks like this, that will contain a sufficient recovery program on it.