I haven't seen the recent creative mixer so I can't give really specific details... but generally the following should work.
1) Go to the creative mixer, in the 'record levels' section, and select 'Line In' as the source. AUX is usually an extra ANSI input connector on the sound card itself, so you can plug in an extra CD-ROM drive or similar device.
2) Plug the line outs of the deck to the line-in on the SB (like it sounds you already did).
3) Load up a recording application. Keep the mixer app open. If you can, turn on 'monitor input levels' or 'monitor' and see if anything registers while the deck is playing.
Since I don't know anything about the software you're using (the mixer and the recorder) I can be any more specific, but it sounds like you did the first stage right already (plugging it in).
It's probably just a matter of selecting the right source in the mixer.
D.