I often need mass-renaming abilities (sometimes Folders, but frequently dozens, hundreds even thousands of Files).
I started with Flexible Renamer 7.3 and still use that even on Win7-64. The later version 8.4 is available with 'official' Win7 sanctioning.
Flexible Renamer is set up in a 3-column format - the Left Column is "Your File-Structure As-Is".
The Middle Column is all of the Renaming Commands and Checkbox Options, plus the data-fields for the new spellings to be entered.
The Right Column is the "Preview Pane" so I can see what my changes will look like. Wonderfully, this displays the changes as I type them.
The Change-To parameters seem fairly complete for my purposes - Search & Replace, plus the ability to Insert or Delete Characters, Numbers, Dates either at the First or Last of a File Name, OR at any X-character distance from those points ("At 4th character from the front, insert SYSDATE" for example).
It also has Date-Attribute Change abilities, too - I can use SysDates or I can hardcode any Date I choose as a new file-attribute (handy for distributing programming updates with one common date).
A great little tool for me but, yes, I've also screwed things up! Even though it has easy Preview Options (a "see the changes as I type them" display) and the typical "Are you REALLY sure?" confirmations, AND it has UNDO functionality, my peabrain will still screw things up.
The amount of Rename Commands IS confusing but the "See As I Type Changes" preview pane helps me understand what "Nth Char From Start" does.