Giga- did you try the auto-configure EXE in the MOHAA directory? It should also be in the start menu with the game\'s shortcut. It\'ll tinker with inernal settings when you switch hardware. When I switched from a Radeon 7500 to a GF4, MOHAA actually ran slower until I ran the AC exe. It still thought my card was a Radeon. :P
If that\'s not the problem then it most likely *is* the Audigy. My friend has a 9700 Pro with an Audigy 2 and all those driver packs Creative make you install sometimes cause incompatability issues. His just rebooted when it felt like it, until he got rid of the Creative drivers.
You could try uninstalling everything Creative, reboot, and say your card is a standard 2-channel card then try and play your games. Or even before that set your audio quality to low to put less strain on the card.