Is a driver bug. Did you go to dell.com, enter your service tag and see if dell has updated any drivers for your machine?
This does not mean they fixed it. Bugs like that are fixed only when enough people report them (and even then not a reason for them to fix it.)
Bob
On this Dell notebook I leave the dual monitor settings, as: Extended Desktop /w notebook as primary (yes I click Apply and OK). Then frequently, though not always, upon rebooting or resuming windows, the setting have changed to Single display with the monitor as primary.
Does anyone know what's up with that?

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