Okay since you have tried it on another computer it seems to be a bad hdd or a bad enclosure. Always good to have an adapter like the Apricorn handy. Keep in mind taking the hdd out of the enclosure voids any warrantys; although, your data may be more important. If it is the hdd, start by running a scan with GetDataBack, if that doesn't work, you can send it off to drivesavers or so on. Their rates start at $500+ depend on how much data you have.