I follow the procedure on how to save your work as described in the book. But when I go back to re-open it I am getting a pop up window telling me that I'm missing audio files. What am I doing wrong?
Did you save your work as Cakewalk Bundle file (.cwb)? or Cakewalk Project file (.cwp)?
If you save as bundle, then all audio files within the project must have been embeded along with the project file.
If you save as project file, then all audio files were stored separately. Have a look inside your audio folder. Are there any files? (You can find the location from Options-->Global-->Audio data-->Global audio folder). To make sure your audio file maintained better, then click on "Use per project audio folder" below it.