And to add to the above.
When you use the installation media, make sure you perform the upgrade from within your current Windows installation.
Don't enter any product key at any stage during the upgrade. It may ask for a product key a couple of times, but just leave the box blank and skip the page.
Also, if you haven't done, make a full image of your system prior to the upgrade. Or at least backup all your important documents, files, photos, videos, music etc etc as an absolute minimum. Although the upgrade should work well, there is always a risk of data corruption and data loss during an upgrade.
Good luck!