Upgrading to Windows 10 is still free. It is a time-consuming endeavor, but if you still want to upgrade your older PC, you can get it here:
Using the Download Tool Now button, you can get a small upgrade program to run on your Windows 7 or Windows 8 PC. As long as the license on your Windows 7/8 is legitimate, this tool will convert that license to a real Windows 10 license as you install. And you will get the option along the way to keep your files and programs.
Now, should you upgrade? Only if you really want to. You’re mostly fine to remain on Windows 7 or 8, as long as you’re happy with your computer, you have valid antivirus and an up-to-date browser (Internet Explorer doesn’t count). I’m providing this information mainly to save people from paying money for Win10 when they don’t have to.
You should NOT upgrade if your computer is running poorly or too slow for your tastes. A Windows 10 upgrade will only make it run slower, or can possibly cause underlying problems to rear their heads.