Windows 7 used the .themepack file extension for its themes, whereas Windows uses a new file extension .deskthemepack. While you can apply Windows 7 themes on Windows 8, Windows 8 cannot be applied on Windows 7.
This is because Windows 8 adds additional support for multiple monitors with a single large wallpaper; and where the images are small, different images are displayed on each desktop. Moreover, themes in Windows 8 now support automatic color change for the windows, based on the primary color of the wallpaper displayed.
In such instances, large panoramic images will automatically extend across both displays of a dual-monitor setup if both monitors have the same resolution settings. If the displays are different sizes or have different resolution settings, a different image will appear in each monitor.
You can also use these panoramic themes on single monitor setups, but only the center part of the image will be visible.
Create Windows 8 theme
This apart, the way to create a theme is the same.
One additional option exists where you need to select the thumbnail to auto-change the windows border colors. You now no longer need to use a 3rd party software to cycle or match the windows border colors. If you don’t want your windows borders to auto-change, select the color you want.
Install Windows 8 theme
Simply use this usual method to create a Windows 7 themepack, and save the theme for sharing. Once you have done that, simply double-click on the theme to install it on your Windows 7.