How you upgraded windows 10?
You may try this link and download the update assistant. You may also burn to 8GB USB drive during this process and use this to update windows 10.
https://support.microsoft.com/en-us/help/3159635/windows-10-update-assistant
Try to use hirens biit cd, it's very good tool to solve a lot of issue,
https://www.hirensbootcd.org/download/
In addition what error message you received when the upgrade failed ? and what is the current error your receiving while trying to boot to Windows 7 again?