Using partition or separate drive as virtual target

[serethos]

I have a Linux Ubuntu system installed on a partition of my harddisk, soon it will be outsourced to its own hard drive.
Now I would like to have the possibility to start Ubuntu from within my host System Windows XP via VirtualBox without
using the Bootloader and a restart - so I tried VirtualBox. But I only see the possibility to create a virtual system using
a virtual drive, but instead I want that the partition/ separate drive is used by the virtualized Ubuntu as if it was started
without VirtualBox. How can I achive this?

[flszen]

Section 9.10 of the User Manual discusses using a raw host hard disk from a guest.