(side note) you might wanna see about removing the blank space in your signature...
(On topic) When you place a data cd into the ROM, does an icon appear on your desktop? If so, can you then click on that icon to access the data cd? I don't quite follow what you have tried to do (or haven't tried) so it's going to kind of be hard to help
Just let us know what you have tried so we can then give you options/suggestions to go with from there.
As for audio CD's, normally linux doesn't mount an audio CD, instead one of the CD playing applications (such as koncd or grip) will simply play them straight from the device.