Try by disabling audio effects.
In order to fix the high CPU usage, you should disable the audio enhancements processed by the audiodg.exe file. To disable the audio enhancements, use the following steps:
- Right-click the speaker icon in the lower right corner.
- Select Playback Devices from the menu. A list of devices should
appear on the screen.
- Double-click the device that has a green checkmark. The properties
windows for that device should open.
- Click the Enhancements tab at the top.
- From the list of enhancements, uncheck all of them, or click the
Disable all enhancements checkbox.
- Click the OK button to save your changes and close the window.
- Click OK to close the Playback Devices window.
The audiodg.exe file hosts the audio engine for Vista. All the DSP and audio processing is performed within this file. Vendors are able to install their own DSP and audio effects into the audio pipeline, which will then be processed by audiodg.exe.
Some audio effects can consume CPU and memory if not properly coded.
Hope this helps.