i agree w/ NL5...straight from NewEgg:
What are the differences between OEM and retail products?
The retail and OEM versions usually will have the same exact product, however the retail version usually will come with bundled software, retail packaging, and more bells and whistles so to speak. OEM (Original Equipment Manufacturer), White Box, Brown Box versions will come with the actual product and sometimes the drivers, but not much else. No special packaging or software. Usually, the retail version will be accompanied by a longer warranty. The OEM version is more for people who build systems and know what they are doing and do not require any extras.
in other words, i would expect the full version of windows to come with more learning tools like Encarta, Microsoft office crap, Disk doctor tools, etc. But I wouldn't know since I just buy the OEM