If I understand correctly, you want to run 2 fully installed OS's at the same time. AFAIK, you cannot run two OS's at once without virtualizing one of them.
So here is what I found on moving an OS from a hard drive to a virtual machine
Convert your Computer into a Virtual
Machine
There's a new
utility from Microsoft that makes it
both simple and free to convert an
existing installation of Windows into
a virtual machine ready to run on any
other computer.
Microsoft’s Sysinternals team has
released a simple application called
Disk2vhd, that lets you easily migrate
an existing computer to a virtualized
hard drive (VHD). It's a tiny utility
doesn't even require instillation.
Create Virtual Hard Disks with
Disk2VHD
When you run Disk2vhd, it will
immediately show you all the drives
and partitions on your computer that
it can migrate to a VHD. Simply
select a drive that you wish to create
a VHD file from and click “Create.”
Disk2vhd will convert the hard drive
into a VHD file even if the computer
/drive is currently in use.
When the Virtual Machine VHD file is
created, you can run it in any desktop
virtualization program including the
free Windows Virtual PC, Virtual Box,
or VMware Player. You can also mount
the virtual machine as a standard hard
drive in Windows 7, and can even boot
from it if your computer is running
Windows 7 Ultimate.
You may use Disk2vhd to create virtual
machines of your Windows XP, Windows
Server 2003, Windows Vista and higher
machines, including x64 systems. Usage
Scenario
Let's say you have a computer that is
already running all the software
programs you frequently use, but you
now want to move to a new computer or
upgrade your operating system. You can
then consider creating a virtual
machine of your old machine using the
Microsoft utility and this will help
you use all your favorite programs
(with the same settings) on the new
machine.
You can also use virtualization to
create a ghost image of your hard
drive in a single file and this will
be handy in the event of a disk
failure.
Disk2vhd is an useful tool that will
make it much easier for you to enjoy
the benefits of virtualization without
being too technical.
From labnol.org
Hope this helps.