I purchased a brand new Mac and upgraded to Mac OS X El Capitan. Then I purchased Parallels 11 Mac because I'd heard about El Capitan incompatibilities. I migrated from my old to my new Mac prior to upgrading and I had owned Parallels 10 prior. I had downloaded and installed Windows 10 Technical Preview and then yesterday I received Windows 10 Pro through the mail on a USB drive. I did that because I had previously attempted an upgrade on this machine to Win 10 Pro using the "free" online version and it indicated that I was not entitled to the upgrade. NOW Windows 10 simply will NOT install over Windows 10 Technical Preview no matter what I do. It goes in a loop, says its upgrading the disk and then does not complete. I am so fed up. I want to know what I need to do in order to make this work. I've followed Microsoft's instructions and they do not work. I tried booting from the USB drive - that wouldn't work. (Introducing the USB, changing the boot order, etc.) I tried installing from within Windows 10 Technical Preview. No installation effort yet has succeeded. What gives? Why will this NOT work? I don't want to lose my apps. My data is fine but I don't want to ask vendors to give me access to software that I've already loaded on the Windows Guest. HELP!