I have a western digital my book 500gb external harddrive and normally the icon for the harddrive would show up in my computer titles 'my book' now it appears in my computer as if it were another internal hardrive, but when i try to open in now is just says it must be reformatted. I've tried a few different computers all with the same problem. i havn't tried actually formatting the drive as it is about full.
you probably have to reformatt it if it says that on all your computer. You mioght of unplugged it without ejecting it first.