WildRename is a user-friendly portable tool that permits you to rename multiple files and more.

You will be able to quickly convert filenames to lower/upper case or normalize case, add/remove strings of characters from filenames, replace strings of characters in filenames using either simple replacements or powerful regular expressions, as well as adding text counters to a series of files. You can also undo files, recurse into the directory tree as well as rename directories

WildRename utilizes the file list and folder tree controls and includes an option for saving of renaming jobs feature as well as HTML help.