So, just installed a GT730 or other HDMI-enabled nVidia video card and now your Dell T7400 has lost audio? Messages like “no output device” or “audio not responding”? Well, after 2 hours of useless searching, finally found that the T7400 BIOS allows 3 settings for the onboard audio: OFF, AUTO, and ON. Turns out that if you set the onboard audio to AUTO, it will disable the onboard audio system if another audio system (such as an HDMI video card) is installed. If you wish to keep the built-in audio working, set the onboard audio to ON and then reboot. Windows 8.1 found it this way, others should as well. Once you reboot, you’ll need to open your Playback and Recording from the System Tray and make sure you direct output to the correct device (not nVidia HD audio).