sound card distorted sound

my computer is one i built myself an amd anthlon xp processor2400+ running at 2.0ghz, a sound blasterLS5.1 sound card with 512mb ddr ram 333mhz a western digital 20gb hd a asus viakt400/333 series mb a nividia geforce2mx400 64mb video card. in the games blackhawk down and blackhawkdown team sabre some times my sound is distorted especially when i am using the team commands and some times it just pops up and distorts when the helicopter is in flight and some times it happens when i am firing a weapon it makes it sound like a laser rather than a rifle or pistol firing bullets. any help will be appreciatd. the sound card is installed and on its own IRQ number with no conflicts and i have the latest driver from the creative website and the onboard audio is disabled.