It is possible that the logic board in the external hard drive housing has gone, in which case you will need to buy a new external hard drive housing. just make sure you buy the right type "SATA or IDE" and size three and a half inch or two and a half inch (laptop). Remove the drive from the existing housing to find out. Some examples here
The other option is to buy one of these
and connect it to a USB port.
If however the hard drive has gone, then you are goosed.