My Book Home 500GB cant read

It started happening a few days ago when the drive would all of sudden seem to go like on a loop where the LED on the front would just keep going up and down like it was being read. I would have to unplug the power, plug it back in and then it would be fine until the next time it does it which would be not long. Then I tried the drive in my laptop but it instantly locked up in the same way. Returned it to my desktop and now it just is locked up with the LED light going up and down like it is being read however the drive doesnt show up in Windows Vista or if it does it shows no files on it. Help.