Hi, I also have dropped my external hardrive while the power was on. Mine however makes a clunking noise on initial start up and then the noise goes away. My laptop does not recognise the external hard drive at all. Any advice much appreciated.
The clunking noise is a dead give away for a damaged drive. If it's under warranty RMA it (don't mention you dropped it). IF it is not under warranty then a data recover lab is probably your only option, (I hate it when people say that to me, but c'est la vie)
"Some" drives can be removed from their enclosure and used inside a PC via SATA cable, that varies from vendor to vendor, but it's doubtful that will work in your case. Good luck.