how to use the virtualisation technology correctly?

On my Win7 Ultimate, i have successfully installed and used a virtual
machine with "XP MODE" actually just for test purposes, i don't really need
a win xp environment.

But what i would like to do is to run a virtual machine from a virtual hard
disk.

Using the MS Backup program that comes with Win7, i created a backup of my
entire machine and as most of you might know, it is possible to "mount" the
backup as a virtual hard drive in Disk Management.

So far so good but i really am now interested in "running the backup virtual
hard drive" in a virtual machine.
This interests me because on some occasions i might want to test some
software, if it does not work or smashes the system, i simply delete the
whole backup and use the previous one.

I have heard that this can work and the Windows Virtual Machines are not
just there for XP mode,
but has anyone succeeded in starting a virtual Win7 machine?

greetings

Roland Schweiger