I got the previous issue and found the mistake I was making. I fixed that problem and got into another issue.

Error message I am getting now is:

$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Importing base box 'udacity/ud381'...
==> default: Matching MAC address for NAT networking...
==> default: Checking if box 'udacity/ud381' is up to date...
==> default: Setting the name of the VM: ud381_default_1491942726306_11989
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
default: Adapter 1: nat
==> default: Forwarding ports...
default: 5000 (guest) => 5000 (host) (adapter 1)
default: 22 (guest) => 2222 (host) (adapter 1)
==> 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", "d95cf3a9-00ce-4106-bdac-2a6ba774a5e7", "--type", "headless"]

Stderr: VBoxManage.exe: error: VT-x is disabled in the BIOS for all CPU modes (VERR_VMX_MSR_ALL_VMX_DISABLED)
VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component ConsoleWrap, interface IConsole