* Reducing the "System Sounds" volume reduces the volume of the screech, without also having to lower the volume of my RealPlayer or Windows Media Center, etc
* The back of the sound card was resting on the hard drive bracket
* I used a cap from an HDMI cable as a spacer to raise the back of the sound card up away from the hard drive
* This hasn't completely eliminated the screech, but it reduced the screech from several per day to a couple per week so I think this solution must be on the right track
* The uploaded picture is here

* Update your PC Bios to the latest and restart the PC

* Try this driver

Disable Enhancements
* Go to Control Panel- Sound
* Right click on the Speaker/Headphones icon and choose properties
* Click on the Enhancements tab
* Select the Disable all enhancements check box
* When finished, restart the PC
 
Disable Wireless A band
* Go to Control Panel- Device Manager
* Click on Networks Adapters
* Double click on the wireless card
* Go to the Advanced tab
* Select from the list Disable Bands
* Select the A band from the list on the right side and disable it
* When finished, restart the PC

LightFX
* Double-click the Dell QuickSet icon in the Notification Area
* Click the LED Effects tab, make sure the Windows Media Player add-in is checked
* Turn off the Smooth color rotation LED effect

Choppy audio might be due to the Secondary IDE CD device being set to PIO. Run PIOtoDMA.exe to set the Secondary IDE CD device to UDMA mode