You realize the fact that you were trying to use USB headphones AND the modem audio simultaneously was probably the conflict?
As such, if you disable the modem, the regular (minijack) headphones won't work, but the USB headphones should. If you have no onboard audio, and no soundcard of any sort aside from the modem, you should use the USB headphones.
Quit screwing with it, disable the modem, plug the USB headphones back in, (since this is the problem you were asking for help in fixing), install drivers for them if needed, and see if the game still crashes.