Restore windows official version

The several installation of windows inside previews from the dev channel, simply made my disk full.

I want to get out of the inside preview and restore the windows to a clean state.

I have read the instructions to do it, and I have realized that this will take time to it. Now, I am afraid of loosing my personal files if I restore windows to a clean state.

Has anyone restored the windows? Did you follow any best practices?