After I have done on the Microsoft website by buying a Windows 8 that I could never activate because it was written in small print on their website that it was necessary already have an earlier version of it I have contacted to procure a full version and they told me that I could not !!!! What's wrong .... I finally found an OEM version on Amazon that I paid the same price as the update. Look for the second error. So if like me you have a Mac and you want to install Windows on it in addition to the OS you should buy this 64-bit version works perfectly.