From KoBoNet Software Develop Team:
Rename It is a simple utility designed specifically for new computer users who are just starting out. This program allows you to easily rename a file or a file extension. Rename It is not only for the new user, more experienced users can utilize Rename It to rename file extensions that Windows Explorer doesn't support. New version features a Massive Rename which can rename many files or extensions easily. Delete function also is available to both single and massive mode.