Windows 7 or 8.1 OEM System builder software is NOT permitted for use on self-build computers or for upgrading an existing OS, or as an additional OS or deploying onto a VM. A Full retail or appropriate retail upgrade version of the OS software must be purchased.
Bizarrely, Windows 8 OEM System builder software IS permitted for use on self-build computers or as an additional OS or deploying onto a VM, but NOT for upgrading an existing OS.
http://www.microsoft.com/oem/en/lice...sonal-use.aspx
If MS are this messed up. it's no great surprise that there's confusion in the minds of the general public.
http://www.howtogeek.com/197232/micr...der-licensing/
SD