The Microsoft told me something so useless that I can't remember. It was about licenses and how VM is different from a regular PC. I did not however ask them about the OEM license, since I already know the answer: "OEM is supposed to be sold with a new computer, its purpose is not upgrading an older system, running on a virtual machine or as a second OS. We have other licenses for that"
See, all of the question are . . . well, not entirely OK legal-wise.