I wrote a tool called "Reng" (Rename Engine) just for this purpose. It does a bunch of things besides renaming/renumbering such as batch file management from multiple locations, use your own custom commands to process files other than the default copy or move (such as image file conversion, bulk zip/compressing, creating masses of shortcut links, etc..), and more. Online help included.
Reng can be downloaded at www.mantom.net in the download area.
Matt
PS - Reng is a command line tool which allows it to be launched from your scripts and other tools.
Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
Matt(at)Mantom.net