Curious about the licensing policies for Virtual PC on Vista?  So was David Berlind.

Here is part of what he found out.  Quoting from his ZDNet Blog:

Q: What type of virtual machine technology is included in Windows Vista?

"Virtual PC Express enables only a single VM. That is key difference between Virtual PC and Virtual PC Express. With the former you can have an unlimited number of VMs and with the latter you can only have one.  Virtual PC Express [will be the version of Virtual PC that's included] in Windows Vista Enterprise and Windows Vista Ultimate."

Q: What happens is the user upgrades to the full blown version of Virtual PC?  One that allows more than just one VM?

"For any additional VMs on the device, customers must purchase retail (otherwise known as shrink-wrap or FPP) copies of the operating system. For the example described above, the volume licensing customer would receive the right to install one copy in a virtual machine. The customer would then purchase 2 additional retail licenses to install in the 2 additional virtual machines (making 3 VMs total). These rights are associated with volume licensing of the operating system rather than with the Virtual PC SKU and so it makes no difference whether the customer is using Virtual PC Express or Virtual PC. "

Q: Is this licensing strictly available to Virtual PC users or can VMware customers take advantage of it as well?

"The secondary install right is associated with volume licensing of the operating system rather than Virtual PC. The customer may chose to install their second instance physically (in a second partition) or in a virtual machine running any vendor's virtualization software. Additional VMs beyond this must be licensed and acquired as stated above."

Read David's entire ZDNet Blog Post, here.