Are you on Windows 7? If so, go into the external and click on "Organize" under the arrow buttons in the top left corner. Go down to "Folder and Search Options", then choose the "View" tab. Under the "Files and Folders" folder, there's another folder for Hidden files and folders." Make sure that "Show hidden files, folders, etc" is checked. Once you can see all the files/folders, right click on them and go in their properties and uncheck "hidden" under the "General" tabs attributes.

If you have a different version of Windows I should be able to help, but if you have a Mac then I kinda have no idea but could help you find a guide for unhiding them?