How to Remove a Windows Watermark With Regedit
Testers of the beta versions of Microsoft Windows' operating systems may notice a small watermark in the lower right-hand corner of the desktop above the Taskbar. This watermark simply displays the beta build version of the system.
If you prefer to run a beta version of Windows rather than purchasing the official release, you may want to remove this watermark. You can do so by making a change in one of the Windows registry entries.
Launch regedit by going to the Start menu and clicking on "Run." Type "regedit" in the field and click "OK."
Expand "My Computer" in the left-hand window. Expand "HKEY_CURRENT_USER." Expand "Control Panel." Click on the "Desktop" folder.
Open the value "PaintDesktopVersion" by double-clicking on it in the right-hand window.
Change the "1" to a "0" in the "Value Data" field, and click "OK."
Close regedit and any other programs and restart your computer.