Yeah, you will have much better success routing the sound from the Mixtrack Pro rather than from your laptop. Find a wire that will allow you to run from the RCA’s in the back of the Mixtrack to your sound system.
Next, make sure the Mixtrack is selected as your audio device ( I really don’t see the point of using ASIO4ALL with the Mixtrack Pro, as it has a built in soundcard that lets you have a Cue Output and a Master Output…) After you have the Mixtrack Pro selected as your audio device, go to your output routing tab in Traktor and make sure internal is selected at the top rather than external, and then make sure Master Output is set to sources 0 and 1 and Monitor Output is set for 2 and 3 ( thats how it is for me anyways). After following those steps it should theoretically work.
If it still doesn’t work check the simple things like: Your sound system is on the right input.. and this may sound stupid but also that the sound is turned up on mixtrack AND the sound system/receiver. I played a gig last night and spent over 10 minutes wondering why no sound was coming out and turns out the receiver was turned almost all the way down :S