oem is $100 dollars cheaper but i found this article that should explain the diffrence
http://www.microsoft.com/australia/g...cs/whatis.mspx
it says the operating system has to stay on the computer u can't put it on another computer
im not sure about this one but i have hered it and im not sure if it is right
(you can't upgrade oem version of a operating system)
once again im not sure about the last part