64-bit VM guests are not listed as option and VM's won't start because of VT-x not available.

[TDslacker]

I had several 64-bit guests (Ubuntu desktop, server, and Windows 2012 R2 server) that ran on my system (Windows 7 ultimate OS, i7 CPU w/16 GB RAM host) successfully with VBox 5.0. I upgraded to Windows 10 and everything broke. I am using VBox 5.0.3 test build now and have gotten my network adapters to work again, but now I'm seeing another issue that is preventing my VM's from running. I can not see a 64-bit guest OS listed as an option (Windows server 2012 isn't listed anymore). This is for my old VM's - they are still have that from when they were running on a Win 7 host but if you look at settings it tries to change it to a 32-bit guest OS and you don't have the option to select a 64-bit guest OS if you try to create a new VM. When I try to start any of my VM's I get an error message about no VT-x available:

Failed to open a session for the virtual machine Anduril.

VT-x is not available (VERR_VMX_NO_VMX).

Result Code: E_FAIL (0x80004005)
Component: ConsoleWrap
Interface: IConsole {872da645-4a9b-1727-bee2-5585105b9eed}

[Frank Mehnert]

VT-x is most likely not available because Hyper-V is enabled for some reason on your Windows 10 host. Try with

bcdedit /set hypervisorlaunchtype off

from a command prompt in Administrator mode.