Rename4u is software that allows you to mass rename any file type. It also gives you several ways to do so. For example, the use of find/replace to rename files with the same extension, the application of a sequence number (ascending or descending), to add a suffix and/or prefix to the new name, to change the case (uppercase, lowercase, etc.). and much more. It includes a test mode so that you can see what the new names will look like before applying them to your files. This software weighs only 70KB and is completely free.