2. Assuming you don't love to use the Windows Media Center, you can fix the audiodg.exe issue by right clicking the volume icon in the system tray (or by going to Sound under control panel) and choosing Playback Devices. Highlight Speakers, then choose Properties. Under the Enhancements tabs, disable all Enhancements. Under the Advanced tab, make sure that you're set on CD quality. You can also kill the Audio Endpoint Builder service by opening your Services by running "services.msc" and stopping the Windows Audio Endpoint Builder Service under its properties. You can also choose to have its Startup Type to remain disabled.
3. The reason you get Access Denied when trying to mess with svchost is because it's a generic, but important process in charge of allowing certain services to run in certain ways at certain times.
4. If you believe that there is no reason what so ever that you believe that you need your Event Logs, in lieu of turning off the service, just go to event viewer (run eventvwr) and Clear/Save each log category under Windows and Administrator logs. You should then alleviate some the processing power that it takes to constantly append mildly large files.