You can't really solve this problem. MANY MANY people have this problem and there is no real solution for it. The best i can come up with is to mute CD audio in windows PLAYBACK mixer.
Mute CD Audio. This wont affect cd playback as windows media and all other players use the Wave section... why? Because MS sucks.
solve your problem. If not, then try reseating the sound card and all your cables. It could also be an IRQ conflict as you said, which is barely possible to solve as well. You could change the PCI slot that your soundcard is in, unless its onboard (OMG! dont get me started on onboard)... then your stuck.