I have a 2009 Mac Pro and created a partition of 200GB on one my HDD so that I can Boot Camp it with Windows 8 Pro. All these versions of Windows is a bit confusing. I need the System Builder version, but there seems to be 2 versions of the System Builder. I called a Microsoft Store and they said they wouldn't trust the OEM version that Amazon is selling. Other stores have this OEM version too, including Micro Center and NewEgg, but I am a little suspicious since the logo for the OEM version on these sites looks a bit strange as it lacks typical marketing slickness. Googling this issue gets me conflicting info: the OEM version has no warranty? OEM gets no support from Microsoft? The version you buy at the store can be transferred to another computer, but the OEM can't? It's the same product but just different license privileges? Right now Amazon sells the OEM for $135, while at the Microsoft Store it's $199, is the OEM version full of bloatware and that's why is cost $65 less?