For those of you out there who have been hankering for a decent free, open-source file renaming utility, I highly recommend that you give Métamorphose a shot. I've been using the v2 beta in XP and it's been excellent. It's written in Python and is also available for Linux, BSD and Macs.
There are a few minor UI bugs though, but I'm sure that they'll be sorted out in due course.
Hooray for FOSS!