I was curious what the difference was between oem and retail version software. Here is what I came up with. The oem version can only be used once on that system and no tech support from M.S. The retail version can be installed in multiple computers, one at a time. Meaning you can install then deinstall then install in another computer. Plus you can call or email M.S. for tech support. Also you get a fancy box and pay $50.00 more for the retail version. Any other thoughts please feel free to add...