Not all games support 5.1 surround sound, check to see if your games support these. (battlefield does) Check for the dolby sign on your games. Your sound card may have a very small hardware buffer, which will explain horrible sound and accelleration. Also check to see if your sound card is encoding in 5.1 in its hardware acceleration mode. (most software for sound cards have this option) It may be encoding 5.1 into 7.1 sound. Those are all possibilities, there are more, but not that I can think of at the time.