Well, since I'm on my old PC now, I can hear exactly what you're talking about.
I optimized this pack for users with newer sound cards, such as SB Live! and up.
I use an Audigy 2 ZS on my gaming machine, and the annoying sound we hear ever 2 seconds or so is an engine cycle effect. These old cards just don't have the fidelity to mix it and display it correctly, thus the annoying "chunk" sound you're talking about.
Low-res sound cards and on-board audio will not do this pack justice.
http://www.newegg.comThey have SB Audigy 2 ZS cards for about $100, if you can spare it. It's worth the price.