Dropped external hdd 2.0 320gb now doesn't work,

Hard Disks are generally VERY fragile, especially the external drives simply because the read/write head inside is a very tiny substance. your case suggests that when it dropped, the read/write head might have got broken, and which means....you might have to get a new one. BUT in a very rare case however..you can do a funny and pretty nice trick, just get another one of the same type (Exactly the same type), then get A Very Good Engineer, and tell him to help you to transfer the read/write head to the former one, just for the purpose of retriving your datas...then return everything back to its normal place. HE HAS TO BE VERY CAREFUL THOUGH!!!, so as not to damage the two hard disks!
(How I wish I could be there to fix it for you, cos I've done it A LOT before...lol).
Hope this solves your problem.