I needed it to be able to boot into the Windows operating system on my Mac, but didn't want the alternative boot from the beginning. There was a specific software I needed to use where the Windows version is considerably superior to the Mac version. I bought Parallels because it seemed to offer this solution. I was not disappointed. It has enabled me perfectly to load the software within the Windows environmental on my Mac and to use it, while continuing to use the rest of my email and other software in the Mac environment. Perfect.