The big difference in the retail and OEM packs is the simple lack of the fancy cardboard carton and paperback manual that goes into details on Windows. That's what you pay $200- more for there. The OEM is the stripped down to disk, booklet, and product key in a small disk holder for those with assumed experience in system building. The full definition on Original Equipment Manufacturer can reviewed at http://en.wikipedia.org/wiki/Original_equipment_manufacturer