If you purchase the software separately, in a package or as a download, the rules are much more liberal. Note that the text for the following rules is identical for retail upgrades and for System Builder software that you install on a PC you build yourself, or in a virtual machine, or on a separate partition. Emphasis in the following sections is in the original:
You may transfer the software to another computer that belongs to you. … You may not transfer the software to share licenses between computers.
In other words, you can remove the Windows 8 upgrade from an original PC and then install it on another PC, assuming the new PC has a license that qualifies it for an upgrade. Likewise, you can completely remove the PUL System Builder software from a self-built PC, a VM, or a partition and then install it in a new physical or virtual PC.
There is no limit on the number of times you may do this type of transfer, providing you follow the rules I describe later in this section. That means hobbyists who like to tinker with PCs can relax. If you buy a System Builder copy, you can move (not share) that license from an old PC to a new one.