Expanding VDI file

Sources

https://www.virtualbox.org/ticket/28
http://www.virtualbox.org/manual/ch08.html#vboxmanage-modifyvdi

http://trivialproof.blogspot.com/2011/01/resizing-virtualbox-virtual-hard-disk.html

http://www.youtube.com/watch?v=VB-nKzTNZS8