First, may I ask why the question is now after the actual question. Doesn't make any sense to me. Anyway....
Just so you don't think I am ten years behind the times, I have purchased a new server with Hyper-V and converting clients to Win 10 Professional. Because Win 7 Pro has a ton of information on it and apps I want to move, I installed another SSD for Win 10 and am using it. It dual boots, so I can go back and forth as necessary. I can't recall why, but I needed to take Win 7 off the domain, then add it again. So, I took it off the domain, made it a workgroup with a local admin, changed the name, then opened a browser and used http://connect
to connect to the domain again. It started, and I got to the point I selected one user, then it gives an error message. I apologize I likely need to get the error message. I believe it was about .NET, so I installed 4.7. Still no luck. Oh, it is trying to connect to SBS 2008. Told you I was behind the times.
While this is a separate issue, it pertains to it, because it can take me ten reboots to get back to Win 7. The only two things in bootup order are the two OS. There are times that during bootup, it shows the whole bar across the BIOS screen, and I can easily select one. However, there are times that it brings me to a GUI, a light blue screen with two rectangular boxes in the upper left, one of which says Win 10 and the bottom one says Win 7. It looks great, but there seems to be no way to move the selection to Win 7 nor stop the clock which is about eight seconds. So, in that instance, it always boots back to Win 10.