I get this error when I'm trying to play a sound in XNA: Error 1 Audio file cash-register.wav contains non-PCM data. What is PCM data?
PCM stands for Pulse-Code-Modulation and is a way to digitally represent analogue (sound) data. The problem you're having is that your WAV file contains invalid data. Did you just rename a .mp3 file to .wav? Or did you use a program to convert the data? If so you should check the converter settings and make sure that only the sound data is converted and that all meta-data is discarded.