We often hear about ESD, OEM and Retail licenses, but what are these licenses actually? What's their difference? Can everyone downgrade? First of all, there are not only OEM and Retail, but: OEM, OEI, Retail, GGK, VL, MAK, KMS, MSDN, Refurbished etc. Some sold digitally (ESD), some canned, some both ways. Let's see them together: read more