Do you have to burn the two different parts in different sessions?
If you want to play the audio on a normal cd-player, you should never use multiple sessions, the mixed mode cd just has the tracks after eachother. first data, then the audio tracks. Use Nero or Easy cd creator for creating them, they have a pretty good manual about it. The Carmageddon 2 cd is a example of an mixedmode cd. fist data, then audio.