OK, so upgraded laptop to Windows 10 from Windows 7. All possible patches and updates installed. Laptop working fine. No issues. Copied OS to Parallels and although virtual machine boots up, when I log in to VM I get "Critical error - start menu and Cortana aren't working. We'll try to fix it when you restart (or whatever it says)'. So restart - nadda! Nothing. Same issue. Spent ages trying to suss out a fix for issue. Googled it and there seems to be lots of people having problems (put not using Parallel, on their equipment) Tried all suggested fixes. Nothing. Upgraded to Parallel 11. No difference. Just can't clear the Critical Error issue. Planning to downgrade Win10 laptop back to Win7, then create a new VM on Parallels of Win7, and then try to upgrade VM Win7 to Win10, to see if that resolves it. Before I start anybody had any similar issues and if so, fixed it. This has already wasted several hours of my life.