If you need to rename several files at once every now and then, this is the application you have always been looking for. Name Mangler is a batch file renamer that supports all common renaming tasks: Find and Replace (including support for regular expressions); Number Sequentially; Change Case; Set Extension; Add Prefix/Suffix; Remove/Insert Characters.
Moreover, you can combine all of these using the Advanced renaming mode, which even comes with some extra features, such as conditional statements, nested counters, and more.