Can't create 64bits virtual machine on VirtualBox

Problem

    I have a exported ubuntu 14.10 64bits that run on VirtualBox.  After I upgrade my host OS (i.e. win7 to win10), that exported ubuntu will crash when I try to boot it.
    Furthermore, when I want to create a new virtual machine, it does not have the "64bits" options.  I know this issue!  Normally, this problem can be solved by Enable the Virtualization Settings in BIOS.  However, I found the Virtualization Settings is still enabled...

Solution

    After several searches, I found this article.  What causes this problem is: Only one virtual machine manager (hypervisor) is valid at a time, but we have Two (one is our VirtualBox, the other is Hyper-V that used by Microsoft (I still wonder if it has to do with the virtual machine of my HoloLens?)).  Although I can't change the settings as the above article did (my OS is win10), the comments of that article provide the solution to turn off the Hyper-V:

bcdedit /set hypervisorlaunchtype off

After typing the above commands in command line and reboot, the VirtualBox can create the 64bits OS and execute it successfully.  However, I found that I should type the above command everytime  I reboot my computer.  Finally, I solve this by removing the "Android-" something that relates to the VisualStudio...