If you need to rename a bunch of file extensions, instead of hunting around for weird programs or doing it by hand, you can just use a tool already built into windows. It’s using the Command Prompt (ie DOS) and it goes like this:
rename *.txt *.wtf
So, that converts all files with the extension (which windows uses to recognize which program will open the file) from .txt to .wtf.
That’s handy, but that means you’ll have to navigate to the specific folder and run the command, which is annoying. What you can do is create what’s called a batch file, is like a little programming/scripting language within Windows. So, I created a text file and renamed it with the extension “.bat” and it has this in it:
REM Replace the m4a with the current file type and the m4b with the target file type
RENAME *.m4a *.m4b
So, all I need to do is copy this file into whatever folder files are, open it and viola, done! As you can tell, I’m using it to change the .m4a audio files to .m4b audiobook files for my iPod. Audiobook files remember the last place you were when you were listening to it while m4a’s are just regular files and would just start all over again. Very handy.
You can download my bat file, here. You may have to right-click on that link and go down to “Save Link As…” or “Save Targe As…”. You can edit it by right-clicking on it and going down to edit. Replace the m4a with the current file type and the m4b with the target file type.