Sound problems

Hi, the problem is that when the screen gets full of laser, effects and sounds; the sound just “breaks” and I get kind of a radio sound when there’s no signal, also a performance decrease and the game starts running like crap, weird since my system is this this: Amd Phenom 9850, 4x1gb ddr2 and radeon HD 4850 512mb.
Still that’s not the real problem since I already solved it by disabling hardware sound (I’ve an audigy sound blaster sound card and I was told that could be causing it), the real problem is that I have to enable/disable it each time I enter the game, if I don’t the problem comes back even tho hardware sound is unmarked on the options, I’ve to enable it again and disable it. What do I’ve to do for it to stay disabled?