Many users who performed a clean install of Windows 10 build 10240 cannot activate it. That is because Microsoft has disabled the online activation until the end of July 2015. If you are interested in activating Windows 10 build 10240, here are a few simple steps for you to do that without using any cracks, hacks or third party software.
As Windows 10 is finalized, Microsoft has released a new build for Windows Insiders. This release is notable and different from previous releases because Windows 10 build 10240 is from the RTM (Release to Manufacturing) branch. So, you will not find a watermark on the desktop in this build and the user experience will be like the final version of Windows 10.