I have a similar problem like mentioned in this question:
Unable to create the virtual machine
But, my problem is a bit different in the error description:
The Windows Phone Emulator wasn't able to create the virtual machine: Something happened while creating a switch: Xde couldn't find an IPv4 address for the host machine.
I have SLAT compatible hardware, virtualization is enabled in BIOS, my Windows 8 installation is 64bit and it's not virtualized. Hyper-V is installed (tried reinstalling it, but it didn't help).
EDIT: VirtualBox or any other virtualization software (except for Hyper-V) is not installed
EDIT2: Seem to have been some other networking software which was installed. Having to remove it sucks big time because I need it professionally. I hope they fix it.
EDIT3: I wrote about it in more details with all I could find on my blog.
Best Answer
It's already answered, but something easier worked for me (and without uninstalling VirtualBox):
"Go into Hyper V. Go into the Virtual Switch Manager. Create a virtual switch called 'Windows Phone Emulator Internal Switch'. Make it's connection type Internal. Now launch the emulator. It should work."
I had to reboot the machine before running the emulator, but now everything's working fine: VS2012, Xde and VirtualBox.
Credits go to TheGeekNextDoor.