So are you using Start Smart / Nero Express(the easiest way) & trying to create an Audio CD or an MP3 CD or what?
And how are you trying to play the CD? On the PC , a standalone player , car stereo etc and what happens?
I don't think that these questions could be much more simply put.
Nero has a Burning ROM facility where you have to specify the type of CD/DVD you are trying to create.
There is also Nero Express which is very much simpler to use. You select the media (CD/DVD) and then what you want to create MP3 disc/Audio CD etc.
These can be accessed via Start Smart which is a program menu effectively.
So just what are you doing?