For the big OEM customers, Microsoft gives them special OEM installation CD/DVD. SN is not required during the installation. It is set by a special program by the worker later, when stickers are attached. The stickers and SN do not work with any retail Windows Installation CD/DVD. If it is a big OEM customers, such as Lenovo and HP, their sticker and SN even do not work with OEM Cd/Dvd from other manufactures.
I bought a second hand HP desktop with windows SN sticker. I tried both retail CD, OEM CD from another computer. They never works for me.
