Here is a free software that enables you to customize the look of your Windows 7 hassle free. Easily change the looks of your Windows 7 Logon Screen, Start Button, Thumbnails, Windows Media Player, Taskbar, Explorer etc. with this ultimate customization tool.
There are many third party portable apps available for download to customize the look of Windows 7. But something we lack was an all in one customization pack. The Ultimate Windows Customizer (UWC) boasts of having several customization options and is the first software in its kind.
Prior to install UWC or any other software you are advised to create a system restore point. In case anything went wrong, you can later revert back your Windows to the previous state.
To Create Windows 7 System Restore Point (it is the second time I am sharing it 
) follow the below steps.
Search for Create a restore point (from Windows 7 start menu) and hit enter.
It will open Windows 7 System Properties dialogue screen. Click Create (check the below screenshot).
Name your back up point and allow Windows to create a back up point.
After creating restoration point as detailed above, download the Ultimate Windows 7 Customizer and unzip its content. Open the folder and click UWC setup.exe file to start the installation. Before running Ultimate Windows Customizer (UWC), if you have tweaked your operating system earlier either manually or by using any other tool, first reverse the changes.
Now start customize your Windows 7. No more manually editing of Windows registry and system files.
The developer offers Windows 8 support soon.
[...] personalisation gallery is rich with wide variety of themes for customization of Windows 7 appearance. They are taking care to update the theme pack gallery with new themes [...]