There are good reasons you *don't* want FCP to decide for you where it thinks the media files are when it can't find them. Let's say you moved the library to another drive and on that drive media files with names Clip0001.mov, Clip0002.mov, etc. already exist. When the moved library is opened, its database says its files are in xyz location, but they're not there. If FCP were to automatically look locally, it might find files with the correct names (and if the same camera was used), frame rates and sample rates and then relink them. Your project would be a mess and you'd have to relink anyway. Much safer and extremely easy to do as Luis says and point FCP to where the media files are and Relink. Takes 3 minutes. This way you're guaranteed that the library references the correct media. For large projects, media management is critical. Hopefully this helps you to understand its importance.