How to setup Ubuntu in Virtualbox and create a VM.
Download Virtualbox Guest Addition ISO images here: http://download.virtualbox.org/virtualbox/.
After installing Ubuntu in Virtualbox on a suitably sized VDI image; add the Virtualbox Guest Additions ISO as a CDROM disk and then start the Ubuntu VM.
Install the build essentials in Ubuntu thusly: sudo apt-get install build-essential to enable you to compile the required kernel modules.
The Virtualbox Guest Additions ISO should be mounted automatically. Navigate to the folder containing the Guest Additions files.
root@hal9000:~# cd /media/homer/VBOXADDITIONS_4.2.16_86992/
Then the Guest Additions files are installed like this.
This will compile and install the required kernel modules that Ubuntu needs to access higher resolutions and copying and pasting between the host and the virtualized operating system.
If you want to use a proper root shell prompt like I am; then use this command: sudo su - that will give you one.
If you forget your password, you can reset it using this guide: http://www.securitronlinux.com/ubuntu-2/how-to-reset-your-password-in-ubuntu-when-running-in-virtualbox/. This is not a very difficult process; you can setup a shared folder to copy files between Ubuntu and Windows.