I have upgraded a couple of machines myself, and the key thing here is to choose the "Upgrade this PC" option on the downloader instead of having it create the installation media. By having it Upgrade using the automated procedure, there is no worry (as long as the host machine's Windows is already activated). Nevertheless, you will need to activate Windows 10 after install, which can be done Online or over the phone (talking to a computer). Also, be sure to choose the bit-depth that corresponds to your current Windows -- unfortunately there is no up-bitting (that I am aware of).