HD audio controller is consuming power during sleep or hibernation in Windows Vista
A hotfix is available for Windows Vista that addresses excessive power use during sleep or hibernation. This problem presents the following symptoms.
If you put the computer to sleep or into hibernation when it is running on AC power, the high definition (HD) audio controller continues to use power. Additionally, even after the computer transitions to DC power while the computer is asleep or in hibernation, the HD audio controller still uses power. This behavior persists even though you disable the “Allow this device to wake the computer” option in the HD audio controller properties.
After you disable the “Allow this device to wake the computer” option in the HD audio controller properties, the Wake on Ring feature still wakes the computer from sleep or hibernation.
Even after you apply hotfix 949514 on the computer, you still experience this problem.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB970030.