The music from iTunes is protected by DRM? You should remove DRM from protected music to mp3 or wav format,or record the music.
If you want to remove the DRM from the CD, you could try Wondershare Media Converter (http://snipurl.com/73txo).
Or you could use DemoCreator (http://snipurl.com/73tvp) to record the music to seperate wav file and then insert the music to PowerPoint.
Steps to insert music to PowerPoint:
1. Display the slide to which you want to add music or sound effects.
2. Click Insert -> Movies and Sounds -> Sound from File, locate the folder that contains the sound file that you want, and then double-click the sound file.
3. In the succeeding dialog box which says "How do you want the sound to start in the slide show", do one of the following:
Click "Automatically" if you want to play the sound automatically when you go to the slide.
Click "When Clicked" if you want to play the sound when you click the sound icon.
Hope these can really help you.
Best wishes.