To enable the internal speaker on the system board, do the following:

1. Replace the contents of the file /etc/modprobe.d/sound with the following:
   
   options snd-hda-intel model=6stack-dig enable=1,1 index=0,1
   # u1Nb.anterc1hhTF:ICH10 HD Audio Controller
   alias snd-card-0 snd-hda-intel
   # kEn8.QkTk4uHneXA:ATI Technologies Inc
   alias snd-card-1 snd-hda-intel
   
   
2. Save the file.
3. Restart the compute. The internal speaker will be enabled.

For ThinkStation S20 4105-38x and ThinkStation D20 4158-29x systems, you can also do the following to configure your system to enable the internal speaker on the system board:

1. Download the script file SetAudio.sh from here to your computer.
2. Open a terminal and navigate to the directory where you have saved the script file.
3. Make sure the script file is executable by typing the following in the terminal: chmod +x SetAudio.sh
4. Run the script file by typing the following in the terminal: ./SetAudio.sh
5. Read the system output carefully and follow the instructions on the screen.