Windows 8.1 and Windows RT 8.1 build on Windows 8 and Windows RT, to bring you enhancements in personalization, search, apps, the Windows Store, and cloud connectivity, and has the security and reliability features you expect from Windows. It's fast and made to work on a variety of devices—especially on the new generation of touch devices.
If your PC is currently running Windows 8 or Windows RT, it's free to update to Windows 8.1 or Windows RT 8.1. And unlike previous updates to Windows, you'll get this update from the Windows Store.
Backup your data and create a restore point.