Can someone help me out with this. I keep reading that an OEM copy can only be "tied" or "licensed" to one machine, so that upgrading, past a certain point, is not allowed. However, if I own the "full" or "retail" version, I can move that license from any one computer to another as many times as I want, providing of course that I don't attempt to run both computers at once. Does that sound correct? Or does Microsoft allow people to move OEM licenses in the same manner? My primary concern is upgrading. If I want to move from a 478 P4 to a 775 Dual Core, just about all the hardware is going to be substantially different, and I am sure I would exceed the number of points that can be changed and trigger a re-activation requirement. I'm not trying to do anything illegal, I just want to know what licensed I need up front so I don't have to keep buying OEM licenses every time I upgrade. Thanks for any help.