
If the process fails, then you can go back to W8.1 via the Macrium Reflect recovery. If you used the Macrium Reflect software to create a system image and bootable recovery drive, the only suggestion I can offer if you are willing, would be to clean install W10 and activate it with your W8.1 product key. Solved: Pavilion 15-p/Window 8.1 to window 10 upgrade - HP Support Community - 8389034 In reference to this discussion a while back.


Notebook Hardware and Upgrade Questions.
