Batch renaming of files

I was trying to search for a certain bit of code in some files in dreamweaver, and was getting frustrated as there were no results, even though I knew the text was there. Turns out that dreamweaver was not searching in files that it didn't recognise (the extension was .men). I tried changing some settings to allow it to recognise the files, which it now does, but it still doesn't search them. Finally decided to change all the extensions to php as I know dreamweaver recognises php files and does search them. Found a nice freeware program that will rename multiple files. It's called The Rename. I downloaded it (2.7MB), installed it, and within 1 minute had renamed all those nasty .men files to .php. Now my searches work.