Hello

Recently, last windows update has been causing some conflicts with the audio driver, you can try updating the Bios and Reinstalling the latest audio/video driver. Also try testing your audio devices one at a time and under audio settings make sure you choose the correct audio device as the default one. If it persists try reverting last windows changes by running a Restore Point to a date before the problem started.

You can find the latest Bios and audio driver for your computer at  support.dell.com and get the latest video driver at http://www.nvidia.com/Download/index.aspx. Let us know how it goes.

Thanks

As you indicate, the problem did seem to appear around the time the "fall creators update" or some such was released - however, the problem persisted even after I did a total reinstall of the OS, and after I updated the Bios.

For the record, I have confirmed that the correct device is selected - this is irrelevant, because as I'm describing, the issue causes the entire audio manager (which you need in order to select an audio device) to become unresponsive, and then act as if entirely disabled.
I only have two audio devices, so there isn't much to test, and I never have both plugged in simultaneously.

In other words - your suggestions have all be attempted and they did not resolve anything.

To summarize:

• All drivers have been reinstalled
• OS has been reinstalled (and with that, all drivers too)
• Sound devices have (irrelevantly) been tested separately, and are exclusively used separately.
• Bios is up-to-date.

Problem persists.

The problem persists, but I have currently seemed to finagle my own temporary "fix" after I installed the Logitech Gaming Software (my headset is a Logitech).
Since installing the software, I can solve the problem when I flick my microphone up and down, which causes the headset to "wake up".

Since installing the software, the problem still does seem to occur randomly, but always occurs when I try to play an online stre@ming video before any other sound has played on the PC.
The problem also seems to always occur when my headset goes into "sleep mode".

Bumping this topic - the problem persists, and windows have even rolled out another update since, as has alienware software.

Bumping again - since last time I wrote, I've found a, more or less guaranteed fix on my end, but it is just a on-the-spot fix and hasn't effectively removed the problem.

Alienware Audio and Nvidia HDMI Audio have nothing to do with audio from a USB Headset.

Windows facilitates the USB Port to work, but that's it.

The USB Headset has it's own "sound card" (in cable) and it's own drivers.