OEM = Originally Equipment Manufacturer
These are items meant to be sold to "Original Equipment Manufacturers" for building/installing in/on a new computer. They are the full version of the product, but lacking certain warranty and/or support features as the person making the computer is SUPPOSED to handle that. That's why they are cheaper - the manufacturer doesn't have to provide as much support for the product. This is perfect for me because I build and sell PCs with OEM loaded on them.
But the OEM version works with pretty much every PC.
