hsafer wrote: What is the right way for me to buy Windows 8 so that I can use it to create a new VM?
Personally I would not upgrade an existing Windows XP Virtual Machine to Windows 8 and instead clean build it. If using Upgrade Media then have a look at "Activate Windows 8 Pro Upgrade" in Windows 8 Upgrade: clean install possible?.
Either purchase an Upgrade DVD or an OEM System Builders DVD. You can also create an ISO Image from downloaded Windows 8 Upgrade from within a Windows XP/7 Virtual Machine and use that to clean install in a separate Virtual Machine.