To remove the annoying activation watermark on window 8 RTM, you have to follow two simple steps.
First, Open a "Notepad" file and write this code with out inverted commas,
@echo off taskkill /F /IM explorer.exe explorer.exe exit
Now save this file as watermark.bat on the desktop
Now Run this file by double clicking on the batch file.
press, Ctrl, Alt, Del simultaneously to start the "task manager" and find the task "Windows Explorer" than right click on it and press "Restart"
Note : If "restart" does not work press "End Task".
Restart your computer (If you press restart on task manager) and enjoy! , you had removed the annoying activation watermark on your windows. Thanks