Windows 7: Batch renaming folders and sub-folders

The structure of my photos library is Y/Y_M/Y_M_D, e.g. 2010/2010_04/2010_04_16 for today.
I want to change all the '_' to '-'.
Does anyone know an easy way of doing this?

You can do it in Irfanview. Heres a couple of tutorials.

Batch

Rename a Series of Files With IrfanView

Thanks, but I can only see how to rename files there. It's just the folders and sub-folders I need to rename.

Maybe it could be done in a DOS command to copy the folders and files, then I could just delete the originals.
As an example I want to change e:\2010\2010_04\2010_04_16\img1234.jpg to e:\2010\2010-04\2010-04-16\img1234.jpg.

File Renamer for Windows 7 - Rename all your files, folders and shortcuts - Windows 7 Download

JoeJoe's freeware utilities - [Rename Master]

And there are dozens more... Google is your friend.

But I would also suggest that your current scheme leads to unnecessrily long pathnames... You are repeating the year 3 times, the month twice in each path. You could do it as YYYY\MM\DD and have a much simpler scheme... Today would then be 2010\04\16... But that's just a thought...

You could use a 3rd party app like renamer. See this page.

How do I ... use ReNamer to batch rename files? | Microsoft Windows | TechRepublic.com

Sorry guys, I'm struggling to see how any of these can rename folders. As you say there are a zillion tools out there for file renaming, but I just can't see how to get them to work on folders.
The first process in them all is 'select files'.

try this.

I found this... but have not tested or used it... no promises...

Fast Folder Rename v1.5 - batch folder renamer :: skyjuicesoftware.com


This one has checkboxes visible for renaming folders... again, untested...

http://www.snapfiles.com/get/flexrenamer.html

Thanks again for all your help guys.
Well, this proved to be a lot more difficult than I imagined it would be! Couldn't get most of your suggestions to work with folders, or couldn't understand the interface, e.g. BulkRenameUtility!
Others needed to be bought for sub-folders to work, etc. etc. I eventually got it done using Fast Folder Rename which is a weird bit of software that needs the files to be dropped into it to work. No real indication of that from the interface.
Anyway, it didn't handle sub-folders, so I had to drag and drop every set of folders into it from Explorer. Only about 150!

CommonTater: I don't use your suggested naming convention because it creates lots of folders with duplicate names, e.g. 16 for today, so searching is more tricky. But thanks for the suggestion anyway.