JSI Tip 5861. Remove 'For Testpurpose only' from your desktop.

Downloads
removeTestpurposeOnly.zip

In tip 5851, I described one reason for the subject display, and how to remove it.

Thanks to Ralf Hofstetter, you can use removeTestpurposeOnly.zip.

Extract PaintDesktop.exe from the ZIP file. When you run it, press the Remove button and restart your computer.