Recently booted up my very old Mac which has Parallels on it as I wanted to run a Windows program. The Mac is running El Capitan with Parallels 10.4.0 which is running Windows 8.1. I can't update the iOS any further than El Capitan and that's fine as I have a new Mac with the latest iOS. Anyway I tried to update Windows from 8.1 to 10 but I got a critical Parallels error and it wouldn't update. I assume 10.4.0 cannot run Windows 10 and I need to update my version of Parallels. The question I have is if I get a new version of Parallels will it run on El Capitan and is it possible to just update the current version of Parallels so I can keep the same virtual machine and not have to create a new virtual machine and therefore lose all my current Windows setup? Updating the Windows version from 8.1 to 10 it is possible to keep everything the same just updated but not sure what the go is with a newer Parallels.