Try it on another computer. If you get the same error than you have lost your files.
An external hard drive should be used to BACKUP your files, not archive them. You should always have at least two copies of important files; I usually have three copies: on two computers and on external hard drive or CD/DVD disc. Despite my own hard drive crashes over the years, I still have copies of files my children made in the early 90s on Windows 3.1. . .