How to upgrade to Windows 10: What you need to know

http://www.pcworld.com/article/2928286/how-to-upgrade-to-windows-10-what-you-need-to-know.html

"Be smart: Make sure all of your important files are backed up before beginning the upgrade process, either via OneDrive or a local external hard drive. By default, your files will remain on the hard drive. “Applications, files and settings will migrate as part of the upgrade, however some applications or settings may not migrate,” Microsoft says, somewhat cryptically."

"Finally, Microsoft will uninstall, then reinstall, your antivirus application. If your subscription is out of date, however, only Microsoft’s own subpar antivirus app, Windows Defender, will be installed. (Microsoft tried this in 2013, then backed off.Be sure and check this after upgrading."