What i've learned by trying out, an oem (slic) system with win 7 homepremium pre-installed will be able to also install/activate starter/basic/prem/pro/ultimate using the correct cert. (i tested this using the multi_oem project files integrated in the iso). PS, a few months ago i reported my vmware 10 pro installs suddenly got HWID activated, never did an upgrade or generated/used a genuineticket on it.
That happens if you install with "Bridged" for network settings, it uses the hosts PID, can easily be replicated
I've only got a Pro Digital Entitlement on my machine, and VMWare activates Pro for me if I use bridged, but saying that, I haven't tested any other configs, but someone else on MDL tried without bridged and it didn't activate, reinstalled with bridged and it did, so...