I am not able to upgrade from Windows 7 to 10 under Parallels 10, build 29105 (Mac Mini 2.6GHz i7, MacOS 10.10.4 with 16GB RAM, 4GB to Parallels). I followed the directions at http://kb.parallels.com/en/122884 as well as attempting from a 64-bit disk image from http://www.microsoft.com/en-us/software-download/windows10ISO. Each time I get about 12% into "Upgrading Windows" when I get a blue screen with an ASCII frown, followed by a resetting to previous Windows version message, followed by a dialog "We couldn't install Windows 10" (see attached screen shot).