I have been experimenting with audacity open source download for making MP3 files for podcasting.
I installed audacity on my laptop and was able to make a MP3 file without a microphone. My laptop was purchased in 2002 and has Windows XP.
If you want a simple way to have your students or children record and make MP3 files, this would be a good way to introduce the process one student at a time.
Technorati Tag audacity