If you want to rename files in one go without having to rename each file individually you should take a look at the free software Renamer NG. Owners of digital cameras for instance will love this software. The camera names the pictures that have been taken Picture001.jpg, Picture002.jpg and so on which is not very helpful if you want to know where the pictures were taken. A file renamer like Renamer NG is capable of renaming all files at once. If you would use the Windows Explorer instead you would soon realize that renaming hundreds of pictures takes a very long time.
