http://forums.creative.com/showthread.php?t=697079
Microphone issues on Windows 7/Vista 64-bit (x64) with 4GB of RAM or more
Audigy driver does not support 64-bit addressing, resulting in random issues with the Microphone (static, robotic or distorted voice, white noise).
Workarounds:
- connect your microphone to your motherboard's integrated HD Audio input
- install the 32-bit (x86) version of Windows
- limit the RAM available to Windows to less than 4GB
- enable Memore Hole in BIOS Setup, if your motherboard supports the setting
последний пункт попробовать, в БИОСе может по другому обзывться, не поможет, менять звук однозначно.