When you see a "SecureBoot isn't configured correctly" message (also known as a "watermark") in the lower-right corner of the desktop, it means that Secure Boot is available, but has either been turned off or set up incorrectly on your PC. Secure Boot helps increase the security of Windows 8.1
and Windows RT 8.1
PCs by stopping unauthorized software from running.
Your PC is probably OK, but it's not as protected as it could be because Secure Boot isn't running.
To set up or turn on Secure Boot, you'll need to use the BIOS menu for your PC, which is a program that starts the operating system when you turn on your PC. Different PCs have different BIOS menus, so contact your PC's manufacturer for instructions. If you're an advanced user and want to explore additional troubleshooting options, go to the Secure Boot isn't configured correctly topic on TechNet.
To remove the watermark without setting up Secure Boot, go to the Update to remove the Secure Boot watermark page.
Be careful when changing BIOS settings. The BIOS menu is designed for advanced users, and it's possible to change a setting that could prevent your PC from starting correctly. Be sure to follow the manufacturer's instructions exactly.