Handy File Tool (freeware).
http://www.handyfiletool.com
File manager program that offers extensive finding, replacing and renaming tools plus more.
I found HFT particularly useful for searching and batch editing text files, of which I have 1000's some of which are huge. It did this many, many times faster than my Windows' built-in Search tool. Makes backups as it goes along just in case you make a mistake (which you can disable).
The interface can take some getting used to and it hasn't been updated in quite a while, but I still find it useful.