As said earlier it should be something such as /books/file.pdf so if your site ishttp://somesite.com the browser will try to loadhttp://somesite.com/books/file.pdf
Currently it tries to access the client side drive which can't work because the file is not on this C: drive. It is on the web server C: drive (and anyway local drive access is blocked by most if not all browsers for safety reasons).
Sometimes it's confusing as when developping, the client side machine and the web server are the same so they have the same C: drive but this is a very particular case.
