Let's say you decided to upgrade your computer to Windows 10 from Windows 7. You need to both install from your computer, and then also create a Windows 10 usb thumb drive (needs to be 8 GB and blank). The install from your hard drive will not require a Windows activation key. Once you upgraded to Windows 10, you can find your NEW key using Belarc Advisor. Either write this new key on a piece of paper or backup to say Google Drive in case your hard drive dies and you need to replace it. The key say on the side of your computer WILL NOT work. I also used google drive to backup some of my data. So if you need to replace the hard drive, you can install from the USB thumb drive by pressing ESC and selecting it from the boot menu. When you are doing a clean install, Windows 10 will ask for the Windows 10 product key. Issues after upgrading to Windows 10 from Windows 7. 1) Printer driver no longer works. Went to Cannon and downloading latest driver, Windows 10 can still not find the printer which is attached by usb cable even after manual install of driver. Only solution is to purchase new all in one laser printer. Looking to get a Wifi printer so all computers and Iphones can connect to it wirelessly. 2) User account that I actually use with my name does not show up as computer went directly into default user account after setup where before both accounts show up at startup. I was able to solve this problem by signing out of the current account (don't shut down) and then seeing my old account which I signed into. I then set a user password for the default account and now both accounts show up at start and default one no longer automatically opens. 3) During startup I did customize setting to turn off all spying but still got adds for Microsoft new version of Office. After using google, found that you can click on that app and nuke it by uninstalling it. 4) Antivirus died but it told me to reinstall it which I did. If there are other issues, I may update this thread.