How do I stop games from overwriting 5.1 sound settings while running?

Every time I start up a game; it overwrites the windows vista 64 sound settings. The sound changes and I the ability to adjust my 5.1 sounds like bass, rear, front and center is limited til non. The games have the 5.1 sound option available, but I'm not able to adjust anything but my 2.1 sounds. For example in Modern Warfare 2 I want to have my bass high for neat explosion effects, but can't raise my bass.

I use a ROCCAT Kave - Solid 5.1 Gaming Headset and have a SupremeFX X-Fi on-board my ASUS Rampage Extreme, X48, Socket-775.

Any help is highly appreciated, thank you