Joe,
"Drew is this an actual VM that runs while the host is running?" YES... can be 1 or more & any or all, depending on RAM, can run @ the same time as the Host Machine. Here, I am not talking about the vhd scenario for dual-booting purposes. Although, that is a terrific approach to dual-booting & certainly, when no virtualization software is in place.
Of course, I am aware of VMware & have attended seminars on it but, I have not used it myself. I had to use VirtualBox to run Windows 8 DP. Previously, I used Microsoft VPC & then Windows VPC ( or was it the other way around )... anyway, as to whether a vm created w/ VMware will run on Hyper-V, I'm sorry, I haven't heard & would have to research that one for you... but, off the top of my head, I very much doubt it. In regard to VMware being free, so is Hyper-V... as was/is MS VPC & Windows VPC. Hyper-V is specific to Windows 8, part of the OS, Pro & higher, just needs a CPU that supports it.
Oh & about the vhd method for dual-booting, that cannot be done w/ version less than Ultimate in 7 & Pro in 8.
But, by using Hyper-V, for example, I have XP, Vista & Windows 7 as VMs, all built on my Win8 HM and I can run 1, 2 or all 3 of them, simultaneously on the HM. The nice thing about leaving them run is Auto Updating & such can happen, same as a physical machine. Moreover that is an advantage over dual-boot. Multi-boot (2 or more) only allows 1 machine to be live @ a time. VMs can all run together, plus the Host; not just one OS @ a time.
Oh and VMs take space... well the VHDs do... so if you create or build more than 1, the drive where they are located needs be large enough to stay 'happy'.
Cheers,
Drew
Link Removed
Sorry, I've not quite answered all your questions but, I trust I've answered some.