You prolly have the "underwater" mixer effect turned on accidently.

If you don't mess with the effects and mixers, then they just run in the background using resources.
Turn off your custom sound mixers that installed during the driver installation of your soundcard or during the addition of other sound apps.
You may see their icons active in the system tray, or spot them in a search of running apps in task manager.
Some may need to be turned off in the startup or possibly even "services" if you use WinXP.
Just another possible angle, hope it helps.

Mainboard: Asus P5K-Premium, CPU=Intel E6850 @ x8x450fsb 3.6ghz, RAM: 4gb PC8500 Team Dark, Video: NV8800GT, HDD: 2x1Tb Samsung F3 RAID-0 + 1Tb F3, PSU: Antec 550 Basiq, OS: Win7x64, Display: 24&