The other day, I decided to upgrade my Windows 8.1 to Windows 10 (on the Insider program, of course). After a couple of days of everything running about as smoothly as I'd expect of an in-development product, I ran into a pretty serious problem with Visual Studio 2015 - namely, that I couldn't use any of the device emulators. Every time I tried to debug a program, I received an error stating "Couldn't change display controller settings of the virtual machine."
After looking online to solve my problem and finding no solutions, I opened up the Hyper-V manager on my machine. I deleted the VM from the list, and re-started the debugging process. After a couple of minutes of resetting the virtual machine, everything works fine now! I assume that some settings from the 8.1 Hyper-V instance or machine are simply not compatible with Windows 10, and deleting and re-creating the VM causes the old settings to get removed and re-created, as well.