It could be worth mentioning relative paths at this point, as these are often a better way to achieve what you often want to achieve by packing; e.g. portability.
If you keep all your linked images, files and folders inside the same folder and set blender to use Relative Paths (User Preferences->File->tick “Relative Paths”) you can rename and move this folder around as you wish without losing your linked files. The added benefit is that any files that are changed, will also be updated in blender.