Okay, so I purchased Kingpin on Monday and I've been playing it ever since. Well, tonight I installed the latest SoundMAX drivers for my ASUS M2N32 SLI Deluxe motherboard. The reason I did this was because I didn't feel as though I was truly getting 5.1 surround sound, my PC actually sounded kind of bad. I had recently re-formatted this PC, so it was missing the proper drivers, apparently. Anyways, my sound problem is fixed and the quality is what I expect it to be....however...
Now the sound in Kingpin doesn't work! I've tried modifying the few sound settings it has available in the Options menu, but to no avail. I've tried tooling around with the SoundMAX control panel (reverting back to just a "Stereo Speakers" configuration, etc). Nothing seems to do the trick. I've tested and if I plug my headphones into the front of my computer case (NOT the speakers), the sound is perfect for Kingpin. So I can still play the game, but it'd be nice if there was an easy fix to get it to work with my motherboard / speakers. I'm using the built-in sound on my motherboard. The speakers I'm using is the Logitech X-540 system.
If anyone has any suggestions, please let me know! Thanks!
Oh yeah, and when I load the game up and I can't hear the sound, well, if I crank my speakers all the way up, I can hear some muffled voices, it's pretty weird, but yeah, not sure if that helps or not.

Also, I purchased Fallout from GOG as well and the sound in it appears to work as expected.

So I figured out that my sound issue was not just Kingpin related, I couldn't get sound when visiting YouTube, MySpace, etc. Come to find out, I wasn't getting sound out of my front speakers at all! Once I figured this out, I decided to just unplug the speakers from my PC and plug them back in. In doing so, SoundMAX detects this action and configures something (or so it says) and that seems to have solved my problem. Not sure what caused it in the first place, but oh well, it's working now!