mp3 playback at lower speed

I'm looking for some program that can play back mp3s at a lower speed than normal. Preferably under GPL or freeware. It may run on a linux box, but would appreciate a Windows version better (some of my colleagues don't run linux).

Thing is that we have a listening exercise for our French final. The fragments are spoken way to fast to understand. -_-
I know it's a bit off-topic, but I thought that you guys surely would know such program.

Thx in advance...