I am trying to upgrade to win10 from win8.1 in my virtual machine. I am running El Capitan 10.11.1 and Parallels 11.0.2. My mac mini has 16megs of physical ram and I have increased the allocation in Parallels to 4GB for this virtual machine. When I try to get the upgrade, the message that I get is that I don't have enough RAM to run Win10. Any idea what is going on?