i just ripped some new cds to aac, and realized that i accidentaly did it with the mp4 extension, not the m4a extension, so my ipod can't read them. is there a batch script or something i could use to rename the extensions on all these files (there're nearly 100 of them) so that i don't have to do it manually?

thx

Open up a command prompt windows and navigate to the directory the files are in (or root directory if they're spread across subdirectories). Then simply type this:

ren *.m4a *.mp4 /s

and hit enter.

you can also use the dbpoweramp's renamer
http://www.dbpoweramp.com/codec-central-utility.htm

thx guys, i used the command line before you posted sani1101, but i'm dl'ing the dbpoweramp thing now

There are tools dedicated to renaming. Try http://file-folder-ren.sourceforge.net/ for example, I use Ant Renamer and I'm quite happy.

Total Commander has a nice mass-rename feature.

There's a tiny little freeware program I use called Extension Changer. You just drop the file or folder and tell it what extension you want. It works wonders. I also use it to send .Rar files over Gmail. I just change them to .Doc or PPS. LOL.