Some Lumia 2520 users may see the following watermark on both the modern UI and desktop interface:

Windows RT 8.1 SecureBoot isn't configured correctly Build 9600

If you see the above watermark, then please check the list of installable updates for a 'Windows RT 8.1 (KB2887595)'.

When using the default settings, the Lumia 2520 will automatically download and install any important updates.

If you would like to manually check for and install any updates, then simply:

  1. 1. Swipe in from the right to open the charms.
  2. 2. Tap Settings.
  3. 3. Tap Change PC settings > Update and recovery.
  4. 4. In the Windows Update page, tap Check now.

For more information on the SecureBoot not being configured correctly, please see:

http://support.microsoft.com/kb/2902864