How to Install Third-Party Themes in Windows 7 with Universal Theme Patcher
Microsoft offer tons of Windows 7 themes and you can download and use those Windows themes for free. However, Microsoft doesn’t allow third-party themes to make major changes to your OS.
You can still manage to do so, by tweaking and patching some system files i.e uxtheme.dll, themeui.dll, themeservice.dll. Universal Theme Patcher is a free utility which patches these 3 files so you can download custom Windows 7 themes and use them on your computer.
Universal Theme Patcher – Patch uxtheme.dll, themeui.dll, themeservice.dll
Download Universal Theme Patcher for Windows 7 (32-bit and 64-bit) from here to patch uxtheme.dll, themeui.dll, themeservice.dll files which will allow you to install and use third-party Windows 7 themes.
Note: This utility requires administrative rights. Turn UAC off before using this.