Windows 10 sees much more monitors than I have

In case someone else is having the same problem, this is what worked for me. I am on an Asus N550JV and the problem occurs only with hyper-V enabled.

Device Manager -> Display Drivers -> right-click on Intel(R) HD Graphics 4600 -> Update Driver -> browse My Computer for driver software -> Let me pick from a list -> Choose the device driver whose version starts with 10.* I have two more options that their version starts with 20.* and neither of them fixed my problem.

You might need to download the drivers from the official site (Intel).

Intel's most recent drivers for this graphics adaptor (version 15.40.37.4835) seem to fix the problem of phantom monitors when Hyper-V is enabled.

On the rare occasions that I have seen this happen before, it is usually caused by the display driver.

Faced with the same scenario, I would manually create a System Restore point as a potential fall-back and then check for an updated graphics driver to install. If you are already running the latest version, try dropping back to an older version and see if it alleviates the problem.