If you have tried to use Windows 10 or Windows 8 theme packs on Windows 7, you may have found that you will not be able to do so. This is because, Windows 10/8 uses a new file extension .deskthemepack, unlike the .themepack file extension in Windows 7. While you can apply Windows 7 themes on Windows 10/8, Windows 10/8 themes cannot be applied on Windows 7.
This is because Windows 10/8 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 10/8 now support automatic color change for the windows, based on the primary color of the wallpaper displayed.
Use Windows 10 theme on Windows 7
But there is a way to use Windows 10/8 themes on your Windows 7.
To do so, download any Windows 10 theme of your choice and right-click on the Windows 10 theme file which you may have downloaded to your Windows 7 desktop, and extract its contents using a free file extraction software like 7-Zip.
The extracted files would be a .deskthemepack file and a DesktopBackground folder which would contain the wallpapers.
Now simply use the 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.
Install Windows 10 theme
To install Windows 10/8 themes, simply double-click on the files. This will install the new theme automatically.