About 6 months ago, I purchased a western digital 500gb external hard drive.  Last week, I accidentally knocked it off my desk while it was attached to the computer.  Now when I connect it to my computer the icon is no longer present to open the hard drive in "My Computer."

Any guesses?  If the hard drive is damaged, is it possible to retrieve files?  I have been directly uploading my digital pics from my camera to the hard drive to avoid filling up my computers hard drive (about 4gb per upload), which means that the files are only on the hd.