|Look in Device Manager for the USB enclosure. There are two components to a USB external hard drive. The enclosure, which is a USB device and should show as such, and the hard drive it self, which you are not seeing anywhere. |
If the enclosure is showing in Device manager then that would indicate it is working. If it doesn't show, that would indicate the opposite.
In which case I suggest you remove the hard drive from the enclosure and connect directly to an internal connection or another USB adapter.
This will void any warranty on the hardware but may allow recovery of the data.
Also, try another USB port or even another computer before taking more drastic steps.