No such thing exists for "normal" people. Volume Copies that do not need CD keys don't even pass the geniune advantage anymore if I remember. When it could pass as ligit it was a pirater's dream come true.
Today it is best to get a retail copy from newegg, bestbuy, or a store of your choice. I am a great fan of MSDN and it's services but you shouldn't become a member just for one operating system.