[NAME] You will video but not sound with the VGA connection, so do not use VGA, use the HDMI connection. I am not sure what you mean by old style/smaller HDMI cables. You should go to Control Panel / Hardware and Sound / Sound and in the Sound window click on the Playback tab and select  P2418HZm and then click Set Default. 
Just purchased a P2418HZm monitor but I can't get any sound from my Studio XPS 8100?  VGA and (old style/smaller) HDMI cables are attached as well as the USB cable that came with the P2418HZm.  Do I need a new expansion card with new style HDMI ports?
Studio XPS 8100, compatibility with P2418HZm?