Reason for the apply button not being clickable because the adjustment you're making is in real time, the apply button isn't necessary. Volume, speaker levels etc, it's like turning a volume knob on a stereo, you don't press an apply button do you, it's similar with PC's. If you were to change sound quality under advanced then the apply button would be clickable.
I've just had a look at your speakers.
http://au.ign.com/articles/2001/09/24/klipsch-promedia-4-1-review That the one?
If it is, it's stereo 4.1 with only two 3.5mm plugs you plug in the back of your computer. It says there in the review, if you want all 4 speakers to work, either use a Y adapter or use one of the rear outputs on the sound card.
Your speakers will not accept 4 individual channels. It is only 2 channel with an additional 2 speakers to make 4. All 4 speakers will play the same thing. It's like wiring two speakers to one speaker wire terminal at the back of a stereo.
Why it's working is you have one of those two wires hooked up to the black port from PC yes?
True 4.1 speakers would have a decoder in the subwoofer to separate signals to front and back. Your speakers is stereo only so you should leave the audio playback to stereo only.
You should have a sub control somewhere on the unit itself and different sound modes. Because these speakers is stereo only, the subwoofer controls from the sub itself, not from Windows.
A creative sound card will not help you. Email them again and include your speaker set. They probably assumed you meant actual 4.1 speakers.
So im not sure how you've hooked your speakers up, if you could explain what you did there would be great, thanks.
Picture of a one to two 3.5mm adapter