Vagrant up - VBoxManage.exe error: VT-x is not available (VERR_VMX_NO_VMX) code E_FAIL (0x80004005) gui headless
<p>Machine: Window10 (64bit).</p>

<p>I downloaded the latest VirtualBox, Vagrant and initialized CentOS 6.7 64bit image/url.</p>

<p>The following worked successfully in Git-Bash session.<br/>
1. vagrant box add "centos67x64" "<a href="https://github.com/CommanderK5/packer-centos-template/releases/download/0.6.7/vagrant-centos-6.7.box" rel="noreferrer">https://github.com/CommanderK5/packer-centos-template/releases/download/0.6.7/vagrant-centos-6.7.box</a>"<br/>
2. vagrant init<br/>
3. Updated Vagrantfile (and turned vb.gui option i.e. uncommented that config section in the file).</p>

<pre><code>  config.vm.provider "virtualbox" do |vb|
    # Display the VirtualBox GUI when booting the machine
    vb.gui = true

    # Customize the amount of memory on the VM:
    vb.memory = "2048"
  end
</code></pre>

<p>After that, I tried the following command but I'm getting this error message.</p>

<pre><code>$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==&gt; default: Importing base box 'centos67x64'...
==&gt; default: Matching MAC address for NAT networking...
==&gt; default: Setting the name of the VM: vv_default_1466548735200_80300
==&gt; default: Clearing any previously set network interfaces...
==&gt; default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
==&gt; default: Forwarding ports...
    default: 22 (guest) =&gt; 2222 (host) (adapter 1)
==&gt; default: Running 'pre-boot' VM customizations...
==&gt; default: Booting VM...
There was an error while executing `VBoxManage`, a CLI used by Vagrant
for controlling VirtualBox. The command and stderr is shown below.

Command: ["startvm", "ae74ebaa-8f01-48cf-bdad-956c59ef1208", "--type", "gui"]

Stderr: VBoxManage.exe: error: VT-x is not available (VERR_VMX_NO_VMX)
VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component ConsoleWrap, interface IConsole
</code></pre>

<p>If I turn/comment off the whole Vagrantfile respective section, I'm still getting the following error.</p>

<pre><code>$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==&gt; default: Clearing any previously set forwarded ports...
==&gt; default: Clearing any previously set network interfaces...
==&gt; default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
==&gt; default: Forwarding ports...
    default: 22 (guest) =&gt; 2222 (host) (adapter 1)
==&gt; default: Running 'pre-boot' VM customizations...
==&gt; default: Booting VM...
There was an error while executing `VBoxManage`, a CLI used by Vagrant
for controlling VirtualBox. The command and stderr is shown below.

Command: ["startvm", "ae74ebaa-8f01-48cf-bdad-956c59ef1208", "--type", "headless"]

Stderr: VBoxManage.exe: error: VT-x is not available (VERR_VMX_NO_VMX)
VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component ConsoleWrap, interface IConsole
</code></pre>

<p>Any ideas! I looked into other posts but couldn't find how to resolve in my case.</p>

<p>As I got some hints, I tried one of the solution.</p>

<ol>
<li>TURN off the Hyper-V which is turned of by default I guess in Windows10.</li>
<li><p>To do this, I Went to Control panel in Windows10 and looked here and found this.
<a href="https://i.stack.imgur.com/cTDpO.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/cTDpO.jpg" alt="enter image description here"></a></p></li>
<li><p>Then, I turned Hyper-V off by unchecking (the tick mark, or black box). </p></li>
<li>Windows10 told me to RESTART, I said "No" (later).</li>
<li><p>Tried running "vagrant up" again (without or without any changes or the above mentioned config.vm... changes to the Vagrantfile). It didn't work and gave me the same --headless error message.</p></li>
<li><p>OK, time to restart. Restarted Windows10. After the restart, I saw bunch of Virtual Box error messages popups (few of them are shown below).</p></li>
</ol>

<p><a href="https://i.stack.imgur.com/uhIaf.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/uhIaf.jpg" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/xnlRu.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/xnlRu.jpg" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/5qyWV.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/5qyWV.jpg" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/zms5k.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/zms5k.jpg" alt="enter image description here"></a></p>

<ol start="7">
<li>Once I clicked on OK button on all of those Virtual Box popup windows, I tried to run Virtual Box on my machine, it came up fine(successfully).</li>
<li>Now, I opened Git-BASH and again went to the directory where Vagrantfile was present. Tried tweaking the settings on / off or commenting/uncommenting the Vagrantfile respective section (as I described above). </li>
</ol>

<p><strong>STILL</strong> getting the the same error messages for running "vagrant up" (even after turning the Hyper-V off as well).</p>