I have an issue where my PC keeps waking from sleep. I have checked the eventlogs and it seems to the be the HD Audio Device that wakes the PC. The PC is a Windows 7 Ultumate 64-Bit edition running on a notebook with no domain, i.e. a normal home PC.
I ran powercfg.exe and got the same responce.
Wake History Count - 1
Wake History 
Wake Source Count - 1
Wake Source 
Instance Path: PCI\VEN_8086&DEV_293E&SUBSYS_13A31043&REV_03\3&11583659&0&D8
Description: High Definition Audio Controller
So I started a cmd.exe with admin privileges, and then tried to disable.
C:\Windows\system32>powercfg -DEVICEDISABLEWAKE "High Definition Audio Controlle
You do not have permission to enable or disable device wake.
I have tried to start the PC in Safe Mode, logonto a true admin account, still same error.