Re: 2 Monitors error

To the guy above, that sounds like your Display Driver crashed, and that also crashes Nvidia's High Definition Audio sometimes for some reason. To verify if that was it, check your EventViewer for display driver crashes under Warnings and then Display. You could also check your Reliability History (do a search for it in the bottom left corner if you're on Win10).

When the display driver crashes along with Nvidia's Sound Driver, it may be the cause for your sound devices defaulting to your monitor. I also noticed this happening a while ago when installing a new Nvidia Driver.

If you manage to confirm the display driver actually crashed, take a look at this discussion: https://answers.ea.com/t5/Technical-Issues/Crash-on-alt-tab-when-using-DX11-native-resolution-w-Full-Screen/m-p/6447532#M3198