USB drive not recognized

Hi, I am hoping that someone could help me out.

I have an external USB drive that is not recognized on 3 different computers (1 running Vista and 2 running XP). I tried plugging it in with the original enclosure and although it lights up & sounds fine my computer won't recognize it under My Computer or Disk Management. Actually my computer doesn't even ding when I plug it in. I removed the HD from the original external enclosure and put in in another one that I have (which I know works) and also different USB cables and get the same results. Is this drive dead? Any suggestions.

Thanks for your help,
Danica