Using VMware Workstation or Player, you can run a virtual machine off a raw disk partition, i.e., not using a vmdk file. Today on Digg we find:
I have my system partitioned into two: one part of the hard drive hosts
a Windows XP partition, and the other runs Gentoo Linux. About a month ago,
I was just about tired of having to reboot to switch between the two, so
I decided to set up a VM for Windows.
There was, however, a snag to this: I wanted to use the existing Windows
installation, because I’d tuned it up and installed the software I always
use. I expressly didn’t want a virtual disk image duplicating my Windows
drive, since I didn’t have the space for that. So, that was the task:
running the Windows partition in a VM.
VMware documentation: Configuring a Dual-Boot Computer for Use with a Virtual Machine.
Many users install VMware Workstation on a dual-boot or multiple-boot
computer so they can run one or more of the existing operating systems
in a virtual machine. If you are doing this, you may want to use the
existing installation of an operating system rather than reinstall it
in a virtual machine.
To support such installations, VMware
Workstation makes it possible for you to use a physical IDE disk or
partition, also known as a physical disk, inside a virtual machine.
Note: VMware Workstation supports booting from physical disk
partitions only on IDE drives. Booting guest operating systems from
physical SCSI drives is not supported. For a discussion of the issues
on a Linux host, see Configuring Dual- or Multiple-Boot SCSI Systems to Run with VMware Workstation on a Linux Host.