If you have Windows 7 and are looking for free themes and backgrounds, desk top gadgets, slide show gadgets, you can get it on the web. Many websites are giving to download for free. But Microsoft also has page where you can download this all, it is Microsoft’s official website.
There is a good tutorial also on how to customize your themes and how to create new themes to share.
There already instructions have been given for how to install themes and gadgets and backgrounds in your PC.
Windows 7 Themes
Slide Show Gadgets