Firstly, I assume the downloaded tunes are .m4a or .aac files if you are saying they are mpeg-4 audio files. If they have a .mp4 extension try re-naming this to .m4a and then import into PhotoVidShow.
Sometimes music brought off itunes may have built in copy protection. In this case these files can not be imported directly into PhotoVidShow. Normally a message will be shown saying this.
The other alternative is that an appropriate codec is not installed on your computer. This is unlikely to be the problem for audio but the solution is to download the ffdshow codec pack from our web site.
It may also be worth trying to convert the audio into another format (i.e. mp3 or wma). This web site does a good job of online conversions. www.zamzar.com/
If the music is protected, all is not necessarily lost. There is a way to “re-record” the music when playing. This is done via the sound card in your computer. i.e. You can record what you here. This will normally be good enough quality to then import back into PhotoVidShow for DVD creation.