A user asked how to install BackTrack in VirtualBox. Since BackTrack is no longer supported and since Kali Linux is a rewrite of BackTrack I opted for Kali Linux.Kali Linux comes with a set of forensic and security tools wrapped in a Linux distro.Kali is designed to assist security experts in determining weaknesses in computer systems.
For an introduction to Virtual Computers see "What is a Virtual Machine?" youtu.be/3QDwKS9JtZY on this channel.
Create a virtual guest for Kali Linux in VirtualBox. Install Kali Linux. Update, upgrade and install dynamic kernel module support in Kali Linux. Install VirtualBox Guest Additions.
Download Kali Linux at: "http://www.kali.org/downloads/". A viewer pointed out that (now 1/1/2015) Kali Linux requires a minimum of 10 GB hard drive space (instead of the 8 GB in the mentioned in the video) but I wouldn't go with less than 20 GB hard drive. Also I would now go with 1 GB (1024 MB) of memory (RAM) instead of 512 MB that was mentioned in the video.