VirtualBox can run whole operating systems "in a window," but that do not have direct access to your computer hardware. VirtualBox can run all versions of Windows, Linux, and various other x86 and AMD/Intel 64 bit systems. Some versions of Linux are optimized to run in a virtual environment, but any will work.
At first, you need to configure and activate the correct repositories to install VirtualBox. Follow the steps:
1. For GNOME, Go to: System > Administration > Software Sources
For KDE, go to: System Settings > Add and Remove Software > Settings > Edit Software Sources
2. Go to "Other Software" tab.
3. Add: deb http://download.virtualbox.org/virtualbox/debian karmic non-free
Now import the package signing key, using the command:
wget -q http://download.virtualbox.org/virtualbox/debian/sun_vbox.asc -O- | sudo apt-key add -
Pretty simple! Run the following command. You may also click on the linked package name:
sudo aptitude install virtualbox-3.1
Now you need to add yourself to the required group. This facilitates access to the vboxdrv system device. Use the following command to add yourself to the required group:
sudo gpasswd -a
Once you have applied this change you will need to logout and log back in. This is required for the group-access change to take effect.
After you are logged back in you should be able to successfully launch VirtualBox from: Applications > System Tools > VirtualBox
Enjoy VirtualBox!! :D
More information: https://help.ubuntu.com/community/VirtualBox