This method wasn't made by me but it hasn't been popularised so I thought I should mention it as many people want to reset Atlas to default.
Atlas as you may know doesn't come with a function to reset back to default Windows like normal Windows does, so I will tell you how to do this
First you will need a Windows 10 ISO file, if you don't know how to get one Atlas actually tells you on the docs here
From here, right click the file and "Mount", or if 7-Zip takes over, extract the ISO into a suitable place. Do not use the GUI because we don't want anything to not work
From here, run "setup.exe" and follow through the options. Hopefully Windows 10 should be installed safely and not Atlas!