Click on Desktop icon settings under the Related Settings section. In the Desktop Icon Settings window, select the Themes tab. Under the Theme section, click on the Desktop button. From the drop-down menu, choose Windows Classic as the theme.
This is a quick guide to enable and use Classic theme on your Windows 8/8.1/10 installation. If you have issues or need help, please see the section below. Methods to Enabling Classic... · Tweaks and Additional Software
Tools used include basicthemer2 for window decorations, secureuxtheme to patch w10 for custom themes, startisback++ for taskbar theming, t-clock to correct ...
I modified moonique's classic theme which is almost identical to niivu's ClassiX theme. I fixed some bugs and changed the navigation and searchbox buttons.