The hidden and system attributes are just that; attributes on files. The obvious system files are those that are installed by windows itself, although I would guess that not all of them are marked as system. Hidden files are also used by the operating system but you could also be have that attribute applied manually if somebody wanted to hide a file from view unless hidden files are being shown by default in Windows Explorer. Whether you back them up or not for a file backup is entirely up to you. You won't get likely unnecessary files like the thumbs.db files which are used to cache thumbnails of images in a folder, but you could be missing other important files like an app that keeps certain important files hidden. So we leave it up to the end user to decide whether or not those files with those flags are important. You can search for them easily in Windows using the ATTRIB command from the command-line. You can research that command if interested.