I have a machine that failed 4 times to update to 10. Each time I tried removing things to make it install. Never did. Now, after the cuttoff date, it’s still trying to install it.
I got into some trouble with my parents windows 7 machine. I blocked the windows 10 upgrade using the standard advice on the web. Windows 7 stopped updating, so I said to heck with it and upgraded to Windows 10. The upgrade was pure hell. The download would stall out after a period of time. The solution was to stop the the windows update service. It will automatically restart by it self. Had to do it 3 or 4 times. Took a couple days out of my life. FUMS...
FYI
When I tried to upgrade from 7 to 10 on an extra hard drive, it stalled out at the point where it said to enter the product code.
Later, I retried installing and ignored putting anything in the new product code blank. It worked. Apparently, it reads the product code from the exiting Win7, but re-inputting the code messes it up.