Read our tutorial on how to back up your system.
At the very least, you should back up all personal files before you begin. It is important that you make a full backup of your system including personal files and folders before upgrading because Windows Updater will empty the installation partition during the upgrade. In this Windows 10 guide, I will show you how to check if a Windows 10 64-bit version is compatible with your PC and how to upgrade from Windows 10 32-bit to Windows 10 64-bit version.